Enhancement of ARM Surface Meteorological Observations during the Fall 1996 Water Vapor Intensive Observation Period

This work describes in situ moisture sensor comparisons that were performed in conjunction with the first Water Vapor Intensive Observation Period (IO P) conducted at the Atmospheric Radiation Measurement (ARM) Program Souther n Great Plains (SGP) Cloud and Radiation Testbed (CART) site during Septemb er of 1996. Two Raman lidars, two Atmospheric Emitted Radiance Interferomet ers. (AERIs), and a suite of 13 microwave radiometers were assembled at the CART site during the IOP. and in situ measurements were used for calibrati on and verification. In addition, this work was meant to help assess the cu rrent observing strategy in an effort to make improvements to the routine c ontinuous measurements. To accomplish these goals, verification of the in s itu measurements was required. Therefore, a laboratory intercomparison of t he in situ moisture sensors (nine capacitive chip relative humidity sensors and four chilled mirror sensors) was performed at the Oklahoma Mesonet tem perature and relative humidity testing and calibration facility. Tests were conducted both before and after the instruments were used in the IOP. maki ng it possible to detect instrument problems prior to the IOP and to determ ine if instrument failure or drift occurred during the IOP. Preliminary results comparing in situ moisture measurements with remotely s ensed atmospheric moisture will be presented and additional applications wi ll be discussed. As a consequence of this work, modifications were made to the ARM CART cali bration procedures. and there are now redundant temperature and relative hu midity measurements so that sensor drift or calibration errors may be detec ted. These modifications: to the observation and calibration strategy led t o improvements in the continuous routine measurements at the ARM CART site.