Structure of momentum and heat flux events in the atmospheric surface layer

Abstract

Time series data of momentum and heat flux, acquired during the monsoon season of 1990 in the surface layer at Jodhpur, Rajasthan, India, are analyzed using a new and simple event detection technique. This technique based on level thresholds in terms of standard deviation, identifies events in the flux signals that account for virtually the entire flux, thus enabling for the first time a full episodic description of the flux time series. Under near-neutral conditions, this description implies that the flow generates positive and negative fluxes over about 35 percent and 15 percent of the time, respectively; at other times, the flow is idle or passive. A strong correlation is found between momentum and heat flux events. The characteristic signature of the events and various statistical parameters concerning them are evaluated.