Journal Club: 09/05/2017

Article Title: Diurnal variations of land surface wind speed probability distributions under clear-sky and low-cloud conditions.

This article examined the impact of cloud cover on diurnal wind speed variability at different heights, from 10m to 200m above the surface, at a mast in Cabauw, Netherlands.  Oberservations from a backscatter ceilometer were used to determine the cloud cover.  Two subsets of the data were isolated using the ceilometer observations, clear-sky (CLR) and low-level cloudiness (LLC).  These were used to partition the wind speed observations.  Wind speed statistics (mean, standard deviation and skewness) were calculated for the two cloud regimes for each season.

Diurnal variability of mean potential temperature (top), mean wind speed (middle) and standard deviation of wind speed for June-July-August CLR (left) and LLC (right) cloud conditions at six different heights (10m, red; 20m, pink; 40m, yellow; 80m, cyan; 140m, green; and 200m, blue).

It was found that the distributions of wind speed as well as the vertical structure of the wind profile tended to vary depending on the cloud conditions.  Wind speeds tend to be stronger and more variable under LLC conditions, compared to CLR.


Thoughts for future research:

– Comparing Cabauw wind speed observations to reanalysis output at different heights.

– Using surface clearness index to partition our data in a similar manner.

– Looking at windrose plots under different cloud conditions.

– Could be relevant to Eadaoin’s research as a method for classifying cloud conditions for her radiation analysis.