zzzAngelaColbert-GrADSresults

=Basic parts:=

1. Download and read...
My language code file for making the below figures is linked here. I started from the code from scratch in GrADS script language.

===2. Calculate zonally averaged P and v over longitude, and plot the resulting latitude-time series.===

Here is the latitude-time sections of P and v in the zonal mean, and at 90W:





When looking at precipitation, it is clear that we do not live at a "typical" longitude, but one that experiences more precipitation than the global average. Whereas the global average precipitation peaks in June, the 90W precipitation has a prolonged peak of similar values in March through November. The most latitudinally extensive peaks in precipitation occur in June and September. This peak in September is most likely from a peak of tropical cyclone activity in the North Atlantic.

When looking at meridional winds, a similar result occurs. The general latitude location and sign (positive or negative) correspond between the longitudinally averaged and 90W meridional winds, but the magnitude is much greater at 90W. There strong southerly winds below the equator are a result of the ITCZ, which is centered slightly above the Equator. The second peak of winds at 90W is from the Antarctic continent and polar winds. Both of these features are seen in the longitudinally averaged field, just with a weaker magnitude.

===3. Average air temperature over both lat and lon, to make a 12-month time series. Which season has the warmest global mean surface temperature? Can you understand why?===

Global mean surface temperature has a mild annual cycle:

As can be seen in the above figure, the global mean surface temperature is warmest in July; however, these changes are minimal. It is important to note that the y-axis of the plot is from 11.5-16 degC, thus the change is approximately 3 degC between the seasons. The reason for the peak in July is that July is the peak of solar isolation for the Northern Hemisphere, which has more landmass than the Southern Hemisphere. Combined with the fact that land has a lower heat capacity than water, the result is a 3 degC peak in temperature in July.

===4. Make a map of the temporal (i.e. seasonal) standard deviation of precipitation, expressed as a percentage of the annual mean precipitation. This might be one definition of a "monsoonal" climate.===

Here is a map expressing the seasonality of precipitation:

Places with intensely seasonal rainfall tend to be over the Saharan Desert (African Monsoon), India (Asian Monsoon), west coast Mexico (North American Monsoon), off the coast of Peru (ENSO?), Northern Australian (Australian Monsoon), and over South Central Africa.

5. What is the space-time standard deviation of 'air' (temperature)?
The total space-time standard deviation of temperature is __**15.2337 degC**__. The challenge of computing it is that we want area averages over the Earth, but we started with lat-lon grids. A simple call of stdev(air array) would give an incorrect answer if the fact that the Earth is on a sphere is not considered. To adjust for this, one needs to verify that one multiplys by cos(lat) for latitudinal averages.