One way to estimate the bias of a particular sounding time in generating a mean daily wind is by simply making more observations per day. While this is not feasible for long periods, pilot balloon observations, because of their low individual cost, can be made frequently for short periods. With these high frequency measurements the bias in inferring mean winds from one observation per day can be estimated. This procedure will be shown to be effective in resolving the diurnal variability of a strong dry season low-level jet (as judged from morning only soundings) over the Venezuelan llanos. We requested twice-daily observations to be made for one month, then made special frequent soundings during a shorter period to resolve the phase of the diurnal cycle of the winds. The details of this activity, carried out in February and March 2003, will be presented. In addition to resolving better the diurnal wind variability as a function of height, the Venezuelan activity consists of observations being made at surrounding sites, allowing us to estimate the horizontal scale of the jet. The steadiness of the dry season jet allows us to extend our conclusions to much of the dry season,; the validity of our conclusions would have to be verified at other times of the year, especially the wet season. Finally, the feasibility of doing this at every sounding site in tropical regions will be discussed.
Supplementary URL: http://www.nssl.noaa.gov/projects/pacs