Rain ‘Creation’ 101

This is strictly a preview. This article is NOT complete.


Rain creation has almost everything to do with the capacity of a land to hold water (in and on the ground, in and on the plants and to a lesser degree; within the air [condensation]). This is the primary way we may influence the density of life giving elements around us. The soil holds the second largest amount of water in California’s environment (and generally), preceded by the atmosphere which holds the most moisture. All followed by plants, specifically trees, who hold the least of the three main water storages. A forests ability to build soil and recycle water is directly related to the local environments temperature and precipitation, irrespectively. Meaning that, terrestrial cycles control meteorological cycles, just as much as the weather controls terrestrial cycles. Other than land catchment and storage of water, secondary influences of rain creation or destruction are out of our immediate control. Things like pollution and macro-scale, planetary changes (el nino, la nina, tectonic plates, volcanoes, ice ages).

The following article displays critical new data from a NASA satellite launched in 2015. This project and its findings have large ramifications for how humans can curb climate change: Study tracks ‘memory’ of soil moisture [Nasa (dot) gov]

If you don’t want to go to this ^ article, I paraphrase here:

A new study of the first year of observational data from NASA’s Soil Moisture Active Passive (SMAP) mission is providing significant surprises that will help in modeling Earth’s climate, forecasting our weather and monitoring agricultural crop growth. They used SMAP measurements to estimate soil moisture memory in the top 2 inches (5 centimeters) of Earth’s topsoils. The estimates improve upon earlier ones that were predicted from models or based on sparse data from ground observation stations. Soil moisture memory, which refers to how long it takes for soil moisture from rainfall to dissipate, can influence our weather and climate.

The team found that, on average, about one-seventh of the amount of rain that falls is still present in the topmost layer of soils three days later. This persistence is greatest in Earth’s driest regions.

The top 2 inches of topsoil on Earth’s land masses contains an infinitesimal fraction of our planet’s water — less than one-thousandth of one percent. Yet because of its position at the interface between land and atmosphere, that tiny amount plays a crucial role in everything from agriculture, weather, climate and even the spread of disease. This thin layer is a key part of the global water cycle over the continents and is also a key factor in the global energy and carbon cycles.

The behavior and dynamics of this moisture reservoir have been hard to quantify and analyze, however, because soil moisture measurements have been slow and laborious to make, or too sparse for researchers to make general conclusions. That situation changed in 2015 with the launch of SMAP, designed to provide high-quality, globally comprehensive and frequent measurements of the moisture in that top layer of soil.

“SMAP’s ability to collect soil moisture data samples every two to three days over the globe gives scientists an unprecedented tool for tracking changes in soil moisture over time,” said SMAP Project Scientist Simon Yueh of JPL, a study co-author. “For the first time, we can accurately quantify these rainfall memory effects on soil moisture on a global scale and for various types of land cover.”

Our ocean, containing 97 percent of Earth’s water, plays a major role in storing and releasing heat. Over land, the moisture in the topmost layer of the soil also stores and releases heat, albeit through different mechanisms. That moisture “is a tiny, tiny fraction of the water budget, but it’s sitting at a very critical zone at the surface of the land, and plays a disproportionately critical role in the cycling of water,” says SMAP Science Team Leader and study co-author Dara Entekhabi of MIT.

Among the study’s other findings, the team found that SMAP data identify regions where soil moisture memory has the potential to influence weather and affect and amplify droughts and floods. When moisture evaporates from wet soil, it cools the soil in the process, but when the soil gets too dry, that cooling diminishes. This, in turn, can lead to hotter weather and heat waves that extend and deepen drought conditions. Such effects had been speculated, but hadn’t been directly studied until now.

Nasa – Full Article


Precipitation – For inland tropical regions, precipitation is basically the measurement of transpired water. For California, atmospheric moisture is mainly sourced from the oceans with only part being caused by regional transpiration. Say you were to copy and paste a full blown tropical rainforest exactly in place of all of California’s forest cover, this forest would obviously degarde very rapidly for a list of reasons. Although, in the first year precipitation would closely shadow the native levels of this rainforest. With this idea in mind, afforestation becomes the main tool to add momentum and density to the regional water cycle. This scenario is ideal for California’s semi-inland, valley orientation. Because atmospheric moisture isn’t lost as much to neighboring regions, due to things like the orographic lift (land induced, atmospheric pressure – A ‘ringing out of the clouds’) of the Sierra Mountain range.

Condensation + Interception – Huge influencer of the entire years water cycle. Has great significance during both the dry and wet seasons. Condensation allows some water for plants on the hottest and driest of summer days. Interception is a forests ability to catch and hold water within the canopy and branches.

Hydraulic Pressure  Healthy valley conditions (water channels included) are at the keystone of a stable watershed. In a crude sense, every inch of eroded earth from a valley floor decreases your entire plane of hydraulic pressure by that same inch. So in a typical Sierra Foothill situation, a waterway stripped down three feet to bedrock, massievly destroys the entire valleys hydraulic pressure and subsequent capacity. Hydraulic pressure is only actionable within uneven terrain. The frequent valleys and water ways of the foothills can easily be restored and plugged. So creek restoration (check-dams, embankments, brush layering…), or formal water management (dams + reservoirs) become absolutely key in forming any permanent hydraulic pressure for the entire region.

Hydraulic Capacity – Specifically, how much organic material is there to hold moisture long-term. As well as tree density and forest height. Plants (trees) store considerable amounts of water in a far more dynamic and useful manner than topsoils.

Evaporation – To drastically reduce evaporation it is important to sustain a closed canopy. pruning and thinning should take place when precipitation is greater than evapotranspiration to keep the ground shaded. The wind is the biggest of evaporative aids, smuggling vast amounts of transpired moisture to surrounding regions. As well as importing moisture from neighboring regions. Windbreaks provide one of the best solutions for reducing evaporation. Either natural breaks caused by neighboring topography or designed rows.

Transpiration/Biological Hydraulic Redistribution (within the soil) – Particularly a trees ability to shuffle and trade water between different depths of the soil profile. In order to handle floods trees exude water up and away, or down and away (depending on soil and plant type). And, droughts cause plants to store water down and away in cool locations, sometimes sharing with neighbors via networks of mycorrhizae fungi.

Watershed – Water channel health, soil health, canopy cover. General resilience for a land to be able to catch and store water, with minimal export.

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