Willis Eschenbach's guest post
Part 1. Research.
I came across a study that has been playing around in the usual climate phase circles. The study's title is
Effects of land use changes and global warming on extreme precipitation patterns in the maritime continent
Here is the summary:
Abstract
Land use changes (LUC) and global warming (GW) significantly affect the maritime continent (MC) hydraulic climate, but their effects on extreme precipitation events have not been responded to. …We found that deforestation caused by Luc increases surface warming, enhances atmospheric instability and prefers local convection, resulting in more frequent precipitation. At the same time, GW expands the hydropower capacity of the atmosphere and further enhances extreme moisture. Our findings reveal the “wet, desiccant” pattern driven by different mechanisms: dynamic processes mainly affect extreme moisture under LUC, while changes in evaporation control are dry. In contrast, at GW, the wet extremes are driven by dynamic processes, while the dry extremes are affected by reduced moisture availability and weakened atmospheric circulation. This highlights the need for land management to address the rising extreme risks.
What is the “Ocean Continent” at home? A good question, never heard of it. Stupid me, I think there are only seven continents. This is what I found.
Figure 1. “Ocean Continent”.
I don't know why the Solomon Islands (grey in the lower right corner) are not included in the “Ocean Continent”. Solo has always been a neglected country in the region. I lived and worked in the Solomon family for eight years, so I had some understanding of weather patterns. Its weather is the same as other weather.
In any case, the area studied is about one-third of the Earth's surface. Additionally, it is located in an unusual place on Earth, called the Pacific Warm Pool, where some of the highest rainfall is found everywhere.
Figure 2. Average rainfall, 1979-2021. Views of the Atlantic and Pacific Ocean. The red box marks the general area of the maritime continent discussed above.
Notice the blue line of heavy rain above the equator. This is rainfall from the semi-permanent band thunderstorm belt in the so-called “tropical Fusion Zone” (ITCZ). ITCZ marks the boundary between the separate cycles of the northern and southern halves of the atmosphere.
Of particular interest are the large blue areas of the Western Pacific and eastern Indian Oceans. This is the area of the “Pacific Heated Pool”. This is the warmest area of the open ocean and the wettest place. This is also the research area chosen by the researchers. For a discussion of the nature of the Pacific Warm Pool, see the post below.
Their study concluded that on the maritime continent (who they don't mention is one third of the surface percentage, in the middle of a warm Pacific pool), wet and dryness is getting dry.
How do they know? Intensive research on rainfall records? Analyze rainfall patterns? What is the correlation between rainfall and the change in El Nino/La Nina?
No. The things that “observe” and “evidence” are the 20th century.
They just ran a few climate models, performed modern stimulation on the guts of the model results, and the answer came out…modern science.
Sadly, although this study covers only a small area in the middle of a unique climate region, the authors can’t help claiming that we are facing “Extreme risks rise“.
Still, my beating heart.
Part 2. Hype
This is research. Then comes the popular report of the study, where it grows significantly in the narrative. There is a typical one below. Following the unbreakable rules of such articles, the title claims that some scientists are worried somewhere. And not just ordinary worries. Existent worry. The bell rings. The title says:
Scientists' discovery of Earth's rainfall is disturbing: “Urgent Need” Shocks
This article basically cites the abstract of the study without attribution, he said:
The researchers say their findings reveal a “wet, dry desiccant” pattern driven by different mechanisms. Dynamic processes largely control extreme moisture under land use changes, while changes in evaporation control dry out extremes. However, in a warm world, dynamic processes expand extreme moisture, and the reduction in moisture and atmospheric circulation can affect the extremes of dryness.
So is it correct to be wet and dry wet on the sea continent or globally? In fact, we have data to determine this. Since 1979, Copernicus has been able to record rainfall from 1° times 1° longitude satellites since 1979.
After reflection, I realized that this is actually two different questions.
•Wet area Gets wet and dry area Become dry?
•Wet Time of year Gets wet and dry Time of year Become dry?
Since we are considering trends, let me talk a little off topic. My assumption is that one of the emerging phenomena of thermal regulation of planets is tropical thunderstorms. Thunderstorms cool the surface in a variety of ways. They make temperatures in Pacific warm pools far exceed 30° to 31°C. Therefore, according to my hypothesis, recent global warming should be accompanied by an increase in cooling rainfall in tropical regions, especially in the very frequent thunderstorms, i.e., the heated convergence zone (ITCZ) above the equator. This is a place that has been getting wetter and drier since 1979.
Figure 3. Rainfall trend. These two panels are the same data as the Pacific and Atlantic Ocean viewpoint. Red line encloses dry areas At -3 mm/ten years or faster at -3 mm. The white line enclosed area is wet at a rate of 3 mm/ten years or more.
Note that this illustrates my assumptions, as thunderstorm-driven cooling is getting higher and higher in the Pacific warm pool and ITCZ. But I digressed into theory. Let me return to observation.
There is something fascinating and surprising about Figure 3. The overall trend is zero. The land is slightly dry and the ocean is getting wetter. Tropical land is drying the fastest, and tropical oceans are getting faster and faster.
Rainfall in New Zealand is decreasing. Around the equator, the largest area for reducing rainfall is between the two largest areas where rainfall increases. North America mostly has no change, except for some dryness on the northwest coast. There are two areas in Nanyang that are getting drier and wetter. Except for the Southern Amazon being drier, most of the world's most properties are very neutral, neither wet and wet.
All of this doesn't see much pattern. Well, except that the actual observations are consistent with my assumption that my assumption is that global warming is an objection to the increase in volume, earlier daily occurrences, and greater cooling tropical thunderstorms.
Keep going, about issues about wet and dryness areawhich is a scatter plot of the decade-year trend of rainfall (vertical axis) with the average annual rainfall (horizontal axis) per 1° latitude relative to 1° longitude Gridcell (n = 64,800).
Figure 4. Scatter plot of a single 1° latitude, rainfall trend and average rainfall, passing through a 1° longitude surface grid ring. The global average rainfall is about one meter, so the “wet” and “dry” areas are based on this threshold.
As shown in Figure 4 above, in areas with less than two meters of rainfall, there is no “wet, drying dryer” at all. It is only humid in very heavy rainy areas, about two meters a year. This is the area we are talking about.
Figure 5. The only humid area in the world is the area where the average rainfall exceeds 2 meters per year.
Note that although most of the “wet” areas are on the ocean, the maritime continental area in the above study is also in the area due to strange coincidence.
This often suggests that regardless of whether 0.3% of the planets they target by targeting the model is the sea continent, Their conclusions do not apply widely to other parts of the earth.
The next question is that it is wet on the ocean continent Time of year Gets wet and dry Time of year Become dry? To investigate this, we can view the standard deviation of the rainfall dataset. If wet and dry, the standard deviation will increase.
So let's start with the actual monthly rainfall on the sea continent.
Figure 6. The average monthly rainfall in the maritime continent.
When people ask what the weather is in the Solomon Islands, I say “There are hot seasons here, followed by wet seasons”. It is no surprise that the Maritime Continent is the same, the Copernicus dataset says. Note that even the driest months on the maritime continent record are around 82 mm higher than the global average monthly rainfall humidity.
Using my marker, I don't see anything “Wet, dryness becomes drier” continue. The biggest fluctuation seems to be in the middle of the record. But let's look at the measurement. This is the 10-year backward standard deviation of marine continental rainfall. Each monthly data point in Figure 7 below shows the standard deviation of rainfall in the previous decade (120 months).
Figure 7. The 10-year lagging standard deviation shown in the maritime continental rainfall data. Each point on the yellow line shows the standard deviation of rainfall data for the previous 120 months.
Again, I didn't see any signs of “wet, dryness gets drier”. There are changes, but no overall trend.
Finally, what happened to the overall rainfall? OK… nothing. This is a global record of rainfall.
Figure 8. Monthly average global rainfall from 1979 to 2024. The trend for the data is 0.05 mm of rainfall increase every decade, which is basically zero.
The ultimate weirdness emphasizes the curious stability of the climate system, i.e. rainfall in the northern and southern hemispheres is also opposed – even if seasonal changes are removed, one hemisphere is wetter and the other tends to be drier and vice versa.
Figure 9. The average monthly global rainfall (black), as well as the northern hemisphere (blue) and southern hemisphere (red).
That's what I know about rain this week. Also, now I know what the Ocean Continent is. As I write this, it rains outside my windows on the generally dry coast of Northern California.
What an amazing planet!
w.
It repeats: When you comment, please quote the exact word you are discussing. I choose my words carefully and I'm happy to explain and defend them. But I can't explain or defend your recapitalization of what you think it means.
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