Commentary by Kip Hansen — 17 August 2023
Let’s talk about droughts. Unfortunately, to do that, we’d have to understand what droughts are. And that understanding doesn’t come easy.
“Drought is a complex phenomenon which is difficult to monitor and define. Depending on the variables used to characterize it and the systems or sectors being impacted, drought may be classified in different types such as meteorological (precipitation deficits), agricultural (e.g. crop yield reductions or crop failure, related to soil moisture deficits), ecological (related to plant water stress that causes e.g. tree mortality) or hydrological droughts (e.g. water shortage in streams or storages such as reservoirs, lakes, lagoons and groundwater).” Alimonti (2022) (currently threatened with retraction due to unscientific pressure from the Climate Crisis Gang)
Or, according to the National Geographic: “Drought is a complicated phenomenon, and can be hard to define. One difficulty is that drought means different things in different regions. A drought is defined depending on the average amount of precipitation that an area is accustomed to receiving.”… “A drought in Atlanta could be a very wet period in Phoenix, Arizona!” (National Geographic isn’t threatened with retraction…though many of its entertainment articles – masquerading as ‘science’ — should be. NatGeo is owned by the entertainment arm of Disney Corporation.)
There are at least 11 types of droughts mentioned at aginfo.in.
The end result of this situation is that there is no single metric capable of determining or representing the presence or absence of drought. Thus, measuring or quantifying something as vague as “number of droughts globally” or “percentage of the world under drought” becomes almost impossible.
Just to give a taste of the sources of possible confusion about droughts, the WestWide Drought Tracker currently offers the following drought images for the western Unites States, all for July 2023:
The maps all seem to agree that it has been or is droughty in the Northwest (Washington, Oregon, Northern Idaho) but there is little agreement elsewhere.
So, when we want to write about “The Drought” in California? Which of these should we use? Which of these did your local newspaper or weather broadcaster use? How and why did he chose that particular one?
It is possible to dig in and find out what each different image is telling us but it is not easy.
What about the U.S. Drought Monitor? They offer this view:
And this:
The two maps are pretty similar, the upper one has the state boundaries and the lower has areas by Drought Intensity and Drought Impacts.
However, it is difficult to find even one of the WestWide Drought Tracker views that look like either of the U.S. Drought Monitor views. Yet they are for the same period (WestWide charts are only a week later than the end of July). How can this be?
Isn’t drought obvious?
The U.S. Drought Monitor [USDM] site tells us this:
“How do we know when we’re in a drought?
“When you think about drought, you probably think about water—or the lack of it. Precipitation plays a major role in the creation of the Drought Monitor, but the map’s authors consider many data sources. Some of the numeric inputs include precipitation, streamflow, reservoir levels, temperature and evaporative demand, soil moisture and vegetation health. No single piece of evidence tells the full story, and neither do strictly physical indicators. That’s why the USDM isn’t a statistical model; it’s a blend of these physical indicators with drought impacts, field observations and local insight from a network of more than 450 experts. Using many different types of data and reconciling them with expert interpretation is what makes the USDM unique. We call it a convergence of evidence approach.”
Let’s be clear: There are some numerical inputs (things that have been measured). There are many subjective inputs: vegetative health, field observations, local insight. Apparently, there are some indicators that are not “strictly physical” that are considered. (What these could possibly be, regarding drought, is a mystery to me…maybe emotional indicators?) All that is then subjected to “expert interpretation” producing “a convergence of evidence”. I don’t mean this as a criticism – I’m simply telling you what the USDM says their maps represent. Maybe this is in response to the problems and confusion caused by the 12 images using differing indices changing over time periods from WestWide? Is it better to have one-drought-image-to-rule-them-all? I don’t know.
And what is the WestWide Drought Tracker? It is brought to us by the University of Idaho, the Western Regional Climate Center, and the Desert Research Institute. They offer many standardized drought indices, each of which is explained on their Overview page. Their site offers:
What products are available on WWDT? (via this page)
Drought Indices (links below are to additional explainers for each)
Palmer Drought Severity Index (PDSI)
Self-Calibrated Palmer Drought Severity Index (sc-PDSI)
Standardized Precipitation Index (SPI)
Standardized Precipitation Evapotranspiration Index (SPEI)
Climate Data (via this page)
Temperature Data and Anomaly (from 1981-2010 normals)
Temperature Percentiles
Precipitation Data and Anomaly (from 1981-2010 normals)
Precipitation Percentiles
All these are involved with the idea of drought. All of them have caveats, for instance: They note that for the Palmer Indices, particularly PDSI, “Snow and its effects are not represented.” NCAR says the PDSI “Does not account for snow or ice (delayed runoff); assumes precipitation is immediately available”. We must remember, they are indicies, each one is an index. All of the indices are calculations, various models, with multiple inputs, many of which are not measurements but parameters.
“What is index in a research project? An index is a composite measure of variables, or a way of measuring a construct….using more than one data item. An index is an accumulation of scores from a variety of individual items.” [source] Or “An index is a type of measure that contains several indicators and is used to summarize some more general concept.” [source]
In other words, an index is a numerical scaling created by combining various factors believed to be integral to the concept – in this case: drought.
NCAR claims that “Maps of the monthly self-calibrating Palmer drought severity index (SCPDSI) have been calculated for the period 1901–2002 for the contiguous United States (20°–50°N and 130°–60°W) and Europe (35°–70°N, 10°W–60°E) with a spatial resolution of 0.5° × 0.5°”. The procedure for calculating the SCPDSI (sometimes sc-PDSI) for any location is given in this paper (see section 2, second paragraph). Count the number of assumed values, parameters, non-measured factors. Raise your hand if you think that climatic records accurate enough for this procedure have been carefully and continuously kept at a spatial resolution of 5° for the entire United States since 1901. How about for the entire world?
In the present day, we are being told “Human-induced climate change has contributed to increases in agricultural and ecological droughts in some regions due to evapotranspiration increases (medium confidence).” IPCC AR6 Chapter 11
With our present confusion in measuring of drought and droughts, it is no surprise that the IPCC has only medium confidence in the above statement and limits its cause to evapotranspiration increases and to some regions. (Is medium confidence a “maybe”, a “might be” or a “probably”?)
So, I have my doubts about droughts. I have doubts that we can accurately ‘measure’ them on any scale other than locally. We can tell when an entire region is in a desperate drought – like the Horn of Africa has currently causing famine or the Southwest U.S. which has been experiencing various levels of drought on a long-term scale but even there, in the desert, some of our indices (SPIs) show a lack of drought. For example, in Arizona.
But there is no line solidly enough drawn – no strict definition — no single dependable scientific metric — that we can use to allow us to determine if there are more or fewer droughts or wider areas of drought – the definitions and even the indices are far too ambiguous for use in any real scientific manner. Mapping and analyzing various indices cannot tell us very much about the world. We can say this or that index is trending up or down but the indices are not real world conditions, the indices are not droughts — they can tell us something, but cannot answer a question such as: Are there more droughts globally now than in the past?
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Author’s Comment:
The same issue affects a lot climate research and data sets. We see graphs and charts of things that are not “real”, not physical — they are like the drought indices, blends of some measurements, some maths, some statistics and some expert interpretations. I am sorry but these are not truly proper fodder for scientific study. Strict science requires actually measuring the thing of interest…not something “sort of like it”.
And we see vast, huge, enormous amounts of time spent analyzing these data sets, many of which cannot possibly be accurate representations of what they are claimed to be. This is as simple as a single weather station’s Daily Average Temperature – it is not the average of the day’s temperature readings at all but the median of the instantaneous high and low. This erroneous data is blended into regional and/or national data bases which then are further averaged, krigged, etc. into even more synthetic data which is also not what it claims to be. On and on….
The moral of the story: keep your eyes open and make sure you ask exactly what has been measured, if it was measured at all, and make sure that you know the implications of the answers those questions.
Thanks for reading.
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Another great post Kip. Very interesting.
gc ==> Thank you. I had to do a lot of digging to find the data . . .
…and, much of what you did find is not really “data”.
Ed ==> Ah, you beat me to it! That is exactly correct — numerical data of an index is not measured data about some climate phenomenon, just as a stage set (backdrops,furniture, costumes, etc) for Othello is not really Venice — if we are lucky, it might make us think of Venice though.
@Kip : “So, I have my doubts about droughts. ”
the lingering doubt is about the unspoken assumption – we are a herd of gazelle looking for water. Are we?
Looking at Africa, the Chad Sea is drying up for decades like the Aral Sea in the Russian Federation, and China is dealing with a huge dry region. Is’nt it strange that the Sahel in Africa, where the latest Niger coup in a long series all involve water and no MSM mentions this?
Look at the Sahara, with petroglyphs of zebra drinking water, today for at least 5000 years dry – is that classified as a drought?
Not being gazelle, we bring water to where it is needed!. The US pioneered this. China is master now. And the Transaqua program for Africa is on the table since 1972.
https://lawrencefreemanafricaandtheworld.com/2022/10/14/nigerian-water-minister-promotes-transaqua-a-water-project-to-save-lake-chad-transform-africa/
bonbon ==> Mankind’s ability to alter the environment to serve its needs explains our success in spreading so widely over the planet, even to places with little water.
bonbon ==> There is much more to the story of Lake Chad than is normally allowed to reach the ears and eyes of the world’s public.
This study from 2019 gives a much fuller picture.
Link does not work
Fran ==> I’ll get it fixed…. Better now….
I think Fran is talking about this one. This study from 2019
When I clicked on it I got a “This site can’t be reached” message.
Fran, Gunga ==> This is the link: https://www.shoring-up-stability.org/
Thanks. The new one works. The old one pointed to this.
” http://this%20study%20from%202019/ “
In my time spent in Colorado, spanning about 4 decades, the irrigation ditches around here have never flowed in August, to my knowledge. They are still flowing strongly and I think they’ll make it into September. The snow fields in the mountains look pretty big for this time of year.
Water must be the key to AGW. Too much or too little both ‘prove’ its’ existence. Just ask them.
I agree with your assessment that tracking drought is complex and difficult, I disagree with the implication that this makes the exercise unscientific. Develop a rigorous definition of the metric you are tracking, and apply it consistently. If you have chosen your variables thoughtfully, your index will provide useful information.
If you believe existing drought indexes are inadequate, propose a new one.
If the chosen metric is not equally, scientifically measurable both in time and location to sufficient accuracy and consistency then it will fail to give meaningful information. Arbitrary adjustments to and in a metric cause it to fail in usefulness. And governments and other organizations maintaining records lie for ideological and political reasons. Always look for the agenda in any presentation.
The challenge lies in using a standardised objective definition of drought.
Even different organisations within the same State often use different criteria.
Something which might prove useful is effective rainfall below the median (for the month) for 3 months or longer. That may not work for very cold areas or highly variable rainfall areas, but could be a useful compromise.
If you believe existing drought indexes are inadequate, propose a new one.
Since the problem is that there are multiple inconsistent indicators already in use, so that a given region is in drought according to some and not according to others, its hard to see how adding another would help.
My conclusion from the piece is not to take assertions about droughts, at least US droughts, at face value. And particularly not with assertions that link supposed droughts to supposed climate change. Because you’re going to be able to take some index to support almost any argument you want to make.
Having multiple inconsistent indicators means you’ve lost falsifiability. That does make doing science on the subject somewhat difficult.
Tulare Lake will once again fill with water.
https://www.ventusky.com/?p=35.4;-111.1;4&l=rain-3h&t=20230821/0300
Ireneusz Palmowski ==> Yes, maybe. Hopefully, Hilary will range further east and dump on Phoenix and the rest of Arizona.
http://www.lightningwizard.com/maps/North_America/gfs_cape_usa72.png
21.08.2023
Ireneusz Palmowski ==> So what do you think? Going to the west or to the east? I can’t see much change so far.
Having lived in the northern Caribbean, on our sailboat, we spent many a nervous day watching hurricane path predictions…in the decade we spent there, landfall location predictions improved quite a bit, but we are still 72 hours out, the limit of any accurate call. In our situation,we had to decide to run for cover (move to a hurricane hole, always required to be within 24 hours voyage during hurricane season)or stay put. The moving option would consume three to four days all told, wasted if unnecessary — but far better safe then sorry. I am here tody writing, so you can tell we always made the correct choices.
It seems to me that the biggest threat will be thunderstorms in the mountains and persistent precipitation. Warm tropical air could melt the rest of the snow in the high mountains.
Thanks Kip. Always enjoy your articles and learn something new.
I’m in the middle of the big red patch in Wisconsin. We did have a dry period from about mid-May through mid-July, but we’ve had plenty of rain since. The corn and soy bean crops showed some stress during the dry period but have bounced back well and look very lush and healthy We’ve had excellent sweet corn for a month now. Rivers, creeks and lakes all at normal levels so I’d say we are no longer and drought at all, but what do I know? Gotta go now and mow the grass for the 3rd time in two weeks.
Rick C ==> But, Rick, you are talking Real World. Your crops are doing well, your grass is growing too fast to keep up with, streams are full and burbling but the U.S. Drought Monitor shows that not only is your area in drought, it is in Extreme Drought. Therefore, your crops and grass must be mistaken (or drought-deniers!).
This is why I have some doubts about droughts…..Some climate scientist will take that map with the red blob (your non-existent Extreme Drought), divide the map up into 5º areas, and declare “Droughts are getting more frequent, worse, and more widely spread.”
Corn and soy beans around the Ruhr and Rhine valleys looked good a couple of weeks ago.
Scissor ==> Eye witness reporting? The trouble with weather is that it is not dependable…it just does what it does.
Yes. I guess I never noticed so much corn being grown in the Netherlands, France and Germany before. It all looked mature and healthy.
Dear Kip,
Droughts are strictly due to a lack of precipitation at a regional scale. The impact of low rainfall is cumulative, and can therefore be assessed using simple tools that take into account potential evaporation (PE), which is a relatively constant forcing, stored soil water from the previous period, and rainfall during the period. Depending on the application, timesteps may be weekly, 2‑weekly or monthly.
Based on ‘rules’ relating to the fraction (f) of water available as the amount held in the soil declines (which approximates the soils moisture characteristic curve), such a water balance can be calculated using Excel. Say for example, for soil that holds 100 mm (4-inches) of available water, the most available fraction (100mm to 75mm) is used at the rate of 0.75 times EP, the next (from 75mm to 25mm), at 0.25*EP, the remainder (<25mm) at 0.1*EP [or variations of that].
The balance is essentially: Water Stored + rainfall – f*EP (minus the excess of the total, less the assumed maximum water holding capacity of the medium, say 100mm). This is called a tipping-bucket or mass balance water balance and it is a handy way of calculating “how much water will be available in the future if” … the if being how much rain can be expected in the next period.
The other approach of using a physical model based on solving Richards equation which assumes certain parameters that describes the movement of water through the soil-atmosphere interface (including runoff, root growth, water take-up, transport through plants, then through leaves and so on) is computationally difficult and hard to parameterize for a particular situation).
I used this approach in a report that I wrote for the NSW Independent Bushfire Inquiry following the fires that burnt-out large areas of eastern Australia in 2019-2020. In addition, I submitted an edited and expanded version to the Royal Commission. The report is summarized here: https://www.bomwatch.com.au/bill-johnston/submission-to-the-nsw-independent-bushfire-inquiry/ and the complete report is available for download (https://www.bomwatch.com.au/wp-content/uploads/2020/06/NSW-Bushfire-Inquiry_FinalRedact.pdf).
Yours sincerely,
Dr Bill Johnston
I should have read further down before I posted my “effective rainfall” proposal in reply to AlanJ.
This is certainly in your area of expertise. The only gremlin is that non-agricultural weather reporting stations may not have any information on soil moisture profiles.
Dear old cocky,
Effective rainfall can be calculated in various ways, my preference is rainfall that equals or exceeds 0.7 times potential evaporation for the period (day, week). The 0.7 is commonly used as the coefficient describing the difference between free water evaporation (Epan) and actual evaporation from soil and surfaces.
Daily time-step Ep is available across Australia either as gridded data or point data from the SILO website. There is probably an equivalent source of data for the US and other places.
I can download data from pre-1900 say for a grid cell, and using that data run a quasi-physical model for a particular vegetation type, which is on my desk-top to gather statistics, or calculate a tipping-bucket water balance say monthly time-step using Excel. As we sold the farm in 2015 I no longer have to worry about when the next shower of rain may happen and what that means for feed-budgeting on a declining autumn/winter feed-base.
As our farm backed onto the escarpment of the Great Dividing Range, I was well aware of the build-up of biomass within the forest and the threat that posed as the landscape progressively dried. The fires were only a matter of ignition and time.
The first fire was the Tathra fire in March 2018, then the Yankees Gap fire in August (which is subject of a current Coronial Inquest), then following those, the fires that swept up from Victoria to Eden and beyond in 2019. (By then we had departed.)
There was an earlier Yankees Gap fire that had us on edge, possibly around 2008 but I’m not sure now. Trying to put fires out after they start, rather than preemptively by hazard reduction, makes spectacular TV-footage with helicopters and tankers buzzing about …. but strewth, the risks and damage to life, property and wildlife are enormous.
All the best,
Bill
That lesson seems to be re-learned after every major fire
Then promptly forgotten 🙁
The Powers That Be must be goldfish
That’s a nice castle
That’s a nice castle
That’s a nice castle
That’s a nice castle
That’s a nice castle
Dr. Johnson ==> Yes, that is certainly one of the formulas used (in general sense) to produced one of the indices used by WestWide. It can be calculated when all the inputs are well known, carefully measured. Many of these are different for each locale. Which is why, for for instance, for some regions that have many different soils, the one approach doesn’t suit — unless there have been a great deal of testing and measuring. The reasons there are so many different indices is that that approach does not fill the bill in every case — if it did, there would be no need for the other indices.
You do good work and I look forward to reading your reports.
Thanks Kip,
Fine tuning parameters often does not result in a ‘better’ outcome, mostly because there are tradeoffs within the methodology and that a perfectly modelled square metre here, may not be the same as another unit-area just over there. Clay may hold more water than sand, but as clay content increases, an increasing proportion of soil water is unavailable – it is held too tightly, which exemplifies the tradeoff between texture and AWC.
I used soil water capacity as a controllable variable – 100mm for mid slope and below, down to 25mm on the top of a stony ridge for example. As the landscape dries, the ridges dry-out first.
As far as drought is concerned, most people close to the land have a ‘feel’ for what is going on. In Australia at least, all climates are seasonal – winter-wet/summer-dry for instance (or vice versa in the north). Of critical interest is whether rainfall during the most reliable months (the months we really depend on) is average or much-below average. Much-below average rainfall in critical months heralds tough times ahead. Two-years running it becomes bloody-tough .. and so on.
While we don’t actually need a water balance, it is a handy budgeting tool, to test scenarios for example. If it looks like staying dry, those who down-stock first will loose less than those forced to race to the exits later with everyone else.
In the report I referred to, while monthly rainfall for Eden is flat through the year (Figure 3), the water balance is highly seasonal (Figure 6). This hides the fact that in winter, daylength is short, temperatures are sub-optimal and so a positive water balance in June is not much use – on average it can’t grow grass. This leads to the idea of a ‘green drought’.
Rainfall occurs as ‘runs’ of wet and dry years – essentially autocorrelation, where wet years tend to follow wet years and vice versa (Figure 6c). Timing of those changepoints is unpredictable and has nothing to do with CO2, coal mining or anything else. Having experienced a few good years, the South Coast of NSW is sliding back into drought (which is the normal state!). Our farm was at Bemboka (see Figure 7),
I also used a streamflow dataset for Tantawangalo Creek at Tantawangalo Mountain to show how this plays-out in a landscape context (Figure 8), and related discharge for the gauge at the top of Brown Mountain to water balance components in Table 1.
Cheers,
Bill
That autocorrelation seems to be tied to underlying large-scale pseudo-cyclical ocean/atmosphere phenomena (ENSO, IOD, SAM). The drivers of these seems to be completely different can of worm, which are still barely known.
You’ve said previously that you were stationed in the Northern Tablelands for some time. Have you done work on the relative effects of these on rainfall in the different regions and times of year?
In very broad terms, ENSO seems to have most effect in the northern half of the country in summer, SAM in the south during winter (without appreciable overlap), and the IOD more in the middle overlapping with both.
Dredging up dim memories from Ag classes back in High School, I vaguely remember that the dividing line between winter-dominant and summer-dominant rainfall was something like Geraldton to Newcastle, but of course that can move as a result of the latitude of the dominant pressure systems.
Ahh, the roads not taken – there are many interesting areas which warrant more than a passing interest.
Dear Old Cocky,
My climate survey work was mainly in the southwest slopes and Riverina of NSW, mostly internal reports – we had no computers then so we had to line-up at NSW Treasury with stacks of punched cards ….
The Geraldton to Newcastle line is about right, but in my later work on http://www.bomwatch.com I was surprised how far north along the WA coast dominance of winter rain persisted (Carnarvon for example experiences winter dominant rainfall (onshore troughs from the sub-polar lows), whereas centres further east experience summer dominant rainfall.) Although I am working on a few more sites, I should re-visit Potshot/Learmonth where I did not include a section on the general climate.
Climate of the east coast is mainly onshore in summer, with low rainfall in winter due to proximity to the Great Dividing Range.
All the best,
Bill
This discussion brings back a lot of old memories, Bill. The years do bury them, so it’s good for them to come up for air now and again.
Ahh, the Good Old Days. That was a little before my professional working life, but the Computer Centre at Sydney Uni had punch cards for the CDC Cyber mainframe. The ribbons barely had any ink left, so we became very adept at reading the characters from the holes punched out of the cards.
I couldn’t remember if it was Geraldton or Carnarvon. Carnarvon seemed too far north so I picked Geraldton. Carnarvon does make sense. On the NSW NW Slopes, we used to get rain off WA NW cyclones.
I’m on the east coast now, but grew up on the NW Slopes. We got some heavy rain at times from Cape York cyclones which came inland to western Qld, then became rain depressions which headed SW.
Alan Wilkie was required viewing in our house, and Dad had a cutting out of an old newspaper with Inigo Jones’s long-range forecasts.
North or south of Latitude 32 degrees south?
While I went to the other one, I still have a Hurlstone badge from a now deceased lifelong friend whom we billeted I think in 1962.
Anyway, while I can’t be definite until I analyse SILO data for Potshot/Learmonth, Carnarvon is probably close to the N-S cutoff for intrusions of moisture from the Southern Ocean. Rainfall distribution for Meekatharra is flat from January to July than cuts-off totally until December (https://www.bomwatch.com.au/wp-content/uploads/2022/12/Meekatharra-December12.FINAL_.pdf). Too much to talk about here.
Unfortunately I’m getting tired of constant analysis and report writing and it’s a long way to the bottom of the list!
All the best,
Bill
(You could contact me via http://www.bomwatch.com.au)
Sydney area now (about 34 degrees) but on the plains out of Narrabri (that would make a good line for a song) growing up – about 30 degrees.
32 is between Gil and Dubbo – yeah, definitely in the transition zone.
Thanks. Yes, I’ll do that.
Woops, there were three. I forgot about Farrer at Tamworth. I don’t think we did interschool sports with them in the 1960s, otherwise they would have never forgotten …
All the best,
Bill
Woops, there were four, Yanco …
Oh, dear. I forgot James Ruse 🙁
I just emailed you.
Nothing like it was in the olden days!
Crops in southeast Alberta and Sw Saskatchewan are not good, dry May and June
“The same issue affects a lot climate research and data sets.”
The use of “data sets” to describe the “global average near surface temperature” anomaly record is inaccurate, probably intentionally.
Data which have been “adjusted” are no longer data, but rather estimates of what the data might have been had it been collected timely from properly selected, sited, calibrated, installed and maintained instruments. Infilled numbers result from the absence of data and do not “become” data. Sets containing actual data, “adjusted” and “infilled” numbers are mixed sets.
Also, there is no such thing as “model data’, merely model estimates which vary depending on the model selected and its beginning assumptions.
Ed Reid ==> Wm Briggs refers to this as “reification” — the pretending or accepting an idea and as real object. Claiming that “The map IS the territory.”
Nothing wrong with spending one’s Saturday downloading gigabytes of KNMI data about an index of something — the error is treating the data that makes up the index as if it were measured data about the physical phenomenon — which it is not.
Ed ==> In general I agree that there is no such thing as “model data” — put it is common these days to refer to the numerical output of models as “model data” to distinguish it from real measured data.
Language is getting trickier and trickier as science veers further and further from the things are are easier to measure. Part of the problem is that we are asking more difficult questions — questions to which we refuse to accept the true answer — which is “We don’t really know.”
My hope is that Colorado benefits from the current El Niño. Based on the drought map, we’re doing okay.
johnesm ==> Well, depends on which index you look at….some of the Westwide maps show Colorado in deep red!
Thanks, Kip, most interesting.
w.
Growing up in India, there was only one important indicator of drought: crop failure. The secondary indicator was wells drying up, but that was usually an indicator of a late monsoon (water table rose and fell annually by about 40′).
Floods were defined by villages being washed away and the number of feet the river rose in the monsoon. The worst was 66′, a once in a century event,and the railway bridge and main north-south road built by British engineers were above that.
Fran ==> Thank you. And, of course, you are absolutely right. For India — the crops told everyone whether there was enough rain/water — no one cared about inches or millimeters of precipitation.
Floods the same — no one really cared about the numbers — the important thing was did the monsoon finally arrive? and were the rivers flooding and washing our villages away.
In the Dominican Republic, where I labored for years, most areas had enough rain,with the exception of “The South” (El Sur). Which was desert-ish and either dry or flooding.
Yeah, Kip. Its tough to take claims of climate emergency seriously when crop yields continue upward, deaths from extreme weather keep declining and normalized damages from extreme weather do not rise over time.
Sitting here in Las Vegas, NV in overcast skies I’m waiting for the howls of climate change being the cause of hurricane Hilary.
Dave ==> Take bets on it — you’ll win.
Yeah, Kip, but the LV casinos are sophisticated enough to apply proper odds to the proposition. The payout would be my bet, less their take.
I see what you mean, but that’s rather too simplistic.
Farmers in regions of variable rainfall have always cared about how much rain they’re getting, and when it falls.
People on flood plains used to care about rainfall and river heights as well.
Both have quite an effect on their lives and livelihoods.
The British in India and all their other Colonies and Protectorates did care about the weather, and were compulsive recorders of temperatures, rainfall, etc.
The early work on the ENSO relationship between the Indian monsoons and the (original) El Nino phenomenon was done by the British in India.
cocky ==>Of course they cared how much rainfall they got — but not the numbers — the farming class had far more practical, ground-truthed considerations. One big rain didn’t help their crops as much as smaller rains spread out over a month, etc — even though, numerically, the monthly rainfall total would appear the same.
Kip, the “when” can be just as important as the “how much”.
I am from the farming class – that’s what the “cocky” means. I can absolutely guarantee you that the numbers are critical in a moisture-limited non-irrigated area.
You can have a sharp shower just on dawn which leaves water lying on the ground and think there’s been a decent fall. Then you check the rain gauge and there’s only been 20 points, which can do more harm than good.
India is monsoonal, but that doesn’t necessarily mean that all the rainfall comes in massive dumps. It’s more likely to be storms which bring a couple of inches, then another storm a week or 2 later.
Rainfall is to a certain extent a proxy for the soil moisture profile, so for small crop-growing holdings you can dig a few holes to check the profile. Much of India was grazing, so that isn’t practical.The grass doesn’t respond immediately to rainfall, so you need to know how much you’ve had to anticipate feed growth. Different plants grow at different times of year, so the timing is also important.
I don’t have experience with places with very regular rainfall, such as England, Ireland or the US New England region. Temperature and day length may well be the critical factors there.
Flood-irrigated crop areas such as the Nile, Tigris and Euphrates would have been quite different as well, with the river floods being the limiting factor.
Yes, a very complicated thing droughts are, because they are literally moving targets.
In its simplest form a drought is a shortfall in precipitation below the average or expected precipitation over some measurable timeframe (weeks, months, years). It is measurable with hard data.
How plants and animals and humans react to drought, however is where it gets very complicated. What may be “drought” to a particular species that was adapted to the average precipitation volume may not be to another species that thrives in a drier climate. Hence a place like the Sahara in north Africa, clearly a very dry desert region today, was at times past a much wetter savanna climate, too wet for desert species. Other areas today that are clearly dry deserts, such as in the American southwest, contain evidence in fossilized species of both plants and animals that in geologic times past, those same places were rain forests, or boreal forests.
Hence species evolve, if the changes are not too abrupt, or else species in adjacent regions migrate into a region that has an increasingly favorable climate.
Finally, short term weather conditions may result in a temporary drought that may impact a particular population or “crop” this year, but if higher rainfall occurs later on, the same populations as before may recover after surviving a period of stress.
But of course the idiot warmunists try to claim that everything is simple, that CO2 is the planet’s sole thermostat … that drought is a simple phenomenon … and that plants and animals do not evolve or migrate geographically to respond to changing climate. All of that complexity and nuance simply overwhelms their simpleton’s minds. In their idiots universe, CO2 = bad, warm = bad, and change = bad. Bad bad bad bad. You must capitulate to their superior “solutions” because everything now is bad … you must give up your freedom to choose for yourself, else we’re all going to die!
Duane ==> Right you are — short-yerm, medium-term, long-term (all with indefitnite terms) and now flash-droughts (derived from flash-floods,I suppose.).. Geologically, there is no such things as drought — only changing local climate to a drier climate type.
Plants and animals in the region of change must adapt, move or die out. If the change is slow enough,they may even adapt/evolve.
Its interesting that fat Westerners are worried about speculative crop failures way out in the future spun by professional liars into an immediate, looming certainty.
The definition of “drought” has become as arbitrary as that of “recession,” “insurrection,” and many other words.
But I think a sensible definition can be reached. Why not just something like “A drought is when the total annual volume of precipitation in a watershed area is less than 40% of the 20-year moving average in that area.”
Certainly if officials tell me an area has had droughts for more than 15 of the last 20 years, I don’t buy it. That’s no drought, it’s a shortage of dams.