Throttleup: Yes, low RH means that respiration of the crop that is up increases. Also, when the air mass is so low in water it is going to be warmer.
Drying of soils etc is much more dramatic when RH is low. Heard on the radio today that in some areas now crops that are up are dying because the roots can't grow fast enough to supply the water needs of the small plants.
The pattern of low RH for this time of year indicates that we are in a dry pattern. That is the most pressing issue.
Another thing that happens is a plant will swell, germinate. The top few inches of soil dry out because of the low RH, and the plant can actually die. Overnight, the soil recovers moisture, but that doesn't help out that plant that is trying to establish itself.
Yesterday RH was 12%. This time of year it is normally in the mid 40% to mid 50% range.
"Sure is hot out! And what better time for a paper to appear in the Journal of Applied Meteorology and Climatology describing the construction of the “all-time” records for various types of weather extremes for each of the 50 United States plus Puerto Rico and the U.S. Virgin Islands. The paper details efforts of the U.S. State Climate Extremes Committee (SCEC) established by the National Climatic Data Center (NCDC) and led by Dr. Karsten Shein. Basically, the SCEC dusted off old records and found other new sources. So now we have “new and improved” data (available here) for the value, the date and the location of the all-time high and low temperature, greatest 24-hr precipitation, greatest 24-hr snowfall and greatest snowdepth for 50 states and two territories. The statewide record extremes have been updated through 2011 and are subject to continuous updating. "
The warmth presently being experienced in the USA is not really exceptional. According to paleo data, what is happening is not close to the MWP, nor the late 1700's. The drought, heat, as evident in the paleo data shows wholesale migration of total Native populations because of this. The cause of the warmth is not known, could be the same cause of our slight warmth now. Who knows?
The hydro cycles seem to play a very important roll in the temp cycles.
"The hydro cycles seem to play a very important roll in the temp cycles."
sigurdur, very well stated. After a year and a half of above normal temps we have experienced a sharp drop off due to nothing other than the number of rainy days and cloud cover. Since June 30 Houston has had only 3 days above 90 degrees which is unheard of for these parts. The high pressure that cooked the upper midwest and east coast has been centered north of us resulting in a rainy wet spring and summer. Hydro cycles play a big role in temp cycles.
Thanks for the info, sig. I am a little smarter now thanks to you. I appreciate all you do. Hopefully, the weather will turn for the better soon.
Another issue with low relative humidity is that the atmospheric enthalpy (energy capacity) is lower. Therefore, less energy is needed to raise the temperature of the atmosphere.
To use an example I have used before: "a misty Louisiana Bayou at 100% humidity after an afternoon storm with the temperature at 78F will hold twice as much heat energy as the air in the Arizona desert at close to zero humidity but at 100F. " So the 'heat records' that are being set may not be 'atmospheric heat energy' records. Temperature is NOT a measure of heat content.