Northwest Abrupt Drying: The Rapid Transition To Dry Out Soils Inwards May

People intend of the Pacific Northwest every bit beingness a wet place, alongside wet, sodden soils.

Perhaps that is truthful during the wintertime as well as early on spring. 

But something startling happens inwards May inwards much of western Washington: a rapid drying of the soils.   

Influenza A virus subtype H5N1 transition thence rapid that some folks start out irrigating their gardens yesteryear belatedly May.

Can this actually last true?   Let's cheque it out.

Here is the soil wet (8 inches down) at Langley, on southern Whidbey island, for the yesteryear month.  Influenza A virus subtype H5N1 major driblet inwards soil wet pct from roughly 26% to around 15%.

Graph courtesy of the WSU Agweather website

Perhaps a improve perspective tin last hit yesteryear looking at the soil wet over an entire yr at this location.  For example, 2017.

Moisture values are high (20-26%) during the winter, exactly inwards May as well as early on June the bottom drops out, alongside values dropping below 8%.  Slow drying follows inwards July as well as August, alongside a huge increment inwards October.

How close 2015, a yr that was peculiarly warm as well as dry?  Again, a large drying inwards May

Looking at other years as well as other western WA stations shows that the May superdrying is a normal occurrence, something that accords alongside my sense every bit a gardener.

But why such rapid drying inwards May?  To understand, 1 must know close an of import meteorological term:  evapotranspiration.  

Evapotranspiration or (ET for short) is the total of evaporation as well as establish transpiration from the Earth's province as well as body of body of water surface to the atmosphere.  Over land, it is mainly H2O evaporating from the earth's surface as well as H2O loss yesteryear plants.  

So ET is the loss, spell atmospheric precipitation is the gain.  If ET exceeds the atmospheric precipitation coming in, surface soil wet declines.

Evapotranspiration is enhanced yesteryear warming of the surface (e.g., yesteryear solar radiations or warm air passing over it), drying of the air higher upward the ground, as well as stronger winds (which assistance mix wet away from the surface).

Think close what is happening inwards May.  

Precipitation is declining rapidly.  Here are average monthly atmospheric precipitation totals at Seattle-Tacoma Airport.  May (roughly 1.75 inches) is a tertiary of the Nov as well as Dec totals as well as less than one-half of the March rainfall.   So much less coming in.

Solar radiation, which warms the surface--promoting evaporation, increases chop-chop inwards May, every bit shown yesteryear the solar radiations for the yr at Langley, WA:

Surface air temperature increases inwards May, relative humidity decreases, as well as soil temperature (which is real of import for surface evaporation ) increases substantially during that calendar month (see below)

In short, a major reject of incoming wet (from precipitation) as well as a large increment inwards evaporation from strengthening solar radiations at the surface as well as warming temperatures, results inwards a rapid reject of solar wet inwards May.  

And nosotros should non forget the large increment of evapotranspiration from plants, which are leafed out as well as growing chop-chop inwards may, sucking out wet from the soil.

Today, I was preparing the soil inwards my garden as well as could non believe how dry out it was.  The May drying has gotten a peculiarly proficient start, alongside drier than normal as well as warmer than normal conditions (see graphs below)

Blue lines is normal precipitation, majestic is this year. 

Red is this year, majestic is normal high, cyan is normal low.

So last prepared to H2O your garden.  And this year, in that location is some other threat to our plants.  Influenza A virus subtype H5N1 real cute, furry threat that has been increasing inwards numbers rapidly:

Influenza A virus subtype H5N1 sign of global warming?  I volition exit that for a futurity blog.