EOS Validation Program

Institution: Univ. of Colorado - CIRES
                    Campus Box 216
                    Boulder, CO 80309
Phone: (303) 497-6192
FAX: (303) 497-6192
E-mail: holger.voemel@colorado.edu

Samuel J. Oltmans, NOAA/OAR/CMDL

February 2003
April 2004

Satellite instruments are crucial for global measurements of upper tropospheric humidity, which has recently received a lot of scientific interest. Currently, the only lightweight balloon borne instrument capable of measuring upper tropospheric humidity is the NOAA/CMDL frost-point hygrometer. We propose to launch balloon borne frost-point hygrometers at 4 different sites: in the equatorial eastern Pacific at San Cristbal, Galapagos, Ecuador; in the subtropical central Pacific at Hilo, Hawaii; at the ARM/CART site near Lamont, OK; and at Boulder, CO. These soundings will provide high accuracy profiles of upper tropospheric humidity in different geographic regions as well as in different seasons. We further propose to launch a new commercial hygrometer to intercompare it with the cryogenic hygrometer. After establishing the vertical range of this instrument, we propose to launch these instruments outside the campaign based validation efforts to provide a larger database for upper tropospheric humidity. The location at San Cristbal, Galapagos, is typically in the down welling branch of the Walker circulation and under clear sky for parts of the year. Frost-point hygrometers have been launched at this site on campaign basis in 1998 and 1999 and ozone sondes are currently launched until the end of 2000. At Hilo, HI, ozone sondes are launched on regular basis and at the nearby NOAA/CMDL observatory on Mauna Loa (MLO), a Raman lidar is capable of measuring upper tropospheric humidity. The ARM/CART site is one of the focuses of the validation effort and we propose to launch frost-point hygrometers during the validation campaigns at this site. At Boulder, CO the frost-point hygrometer has been launched for 20 years and we propose to launch hygrometers at this site during later stages of the validation effort.