CLEX OBSERVATIONAL STRATEGY

As can be noted from the discussions and the results in Section 2, the CLEX - the observational campaigns planned during the June 1996 - April 1997 period - crosscuts all three scientific questions being addressed in Task 10. Science Questions No. 1, addressing cloud base and layer estimation from present-day passive remote sensing systems, clearly needs and extensive layer cloud validation data set the field experiment will provide. Question No. 2 dealing with incorporation of these clouds and their effects into developing numerical forecast models needs the new observational data set for several key diagnostic studies. Question No. 3 on the relative role of radiative heating/cooling in both

observational cases over land regions having good co-relative data on wind fields, moisture profiles, etc. The planned observational experiment over the Eastern Colorado-to-Oklahoma and the California coastal regions would be a DoD Center for Geosciences collaboration with NASA (their DC-8). JPL (their new airborne cloud-profiling radar), the DoE's Atmospheric Radiation Measurement (ARM) program (their in situ and ground remote sensing site on the OK-KA border), NOAA (segments of its research laboratories and its Wind Profiler, ASOS, and rawinsonde network), and other collaborators. The planned experiment will not only meets the needs of Task 10 research but will also provide special validation needs of Task 5 (cloud liquid water over land research) and Task 8 (multi-sensor remote sensing of water vapor research).

Furthermore, the CLEX will provide a good opportunity for the first scientific flights of the NASA/JPL Airborne Cloud Radar. Layered cloud/radiative interactions are important factors in NASA's Mission to Planet Earth/Climate System research.

Therefore, the observational strategy for CLEX has been developed to optimize airborne, satellite and ground-based observational resources while maintaining a close focus upon the scientific objectives of Section 2. To do this we have established a real-time cloud/weather science operations center. We also plan and good communications links among:

(a) the CSU/Fort Collins, Colorado science operations center;

(b) the NASA/JPL DC-8 Cloud Radar experimenters;

(d) the CSU/DRI ground-based observing site at the DoE/ARM site in Oklahoma.

Furthermore, we have arranged for special satellite coverage and data collection via NOAA/NESDIS and the CSU/CIRA Satellite Earthstation. We have also arranged for real-time collection of:

(a) ASOS and SAO data;

(b) normal and special rawinsondes;

(d) operational analyses and forecast products from NCEP and ECMWF.

As is noted in the timeline in Section 4, we have identified a CLEX-1 time period from mid-June to early July as the time to optimize observational assets. Our interests lie primarily over the Central Great Plains where we expect layer-cloud system occurrence free from lee of the mountain and/or other major surface effects. A region from approximately 34-43N and 94-105W will enclose CLEX-1 observations and will provide a regional weather data "boundary."