# Presentation: 358601

## Comparison of Airborne Sunphotometer and Near-Coincident In Situ and Remotely Sensed Water Vapor Measurements during INTEX-ITCT 2004

- J. Livingston1, B. Schmid2, J. Redemann2, P. Russell3, S. Ramirez2, J. Eilers3, W. Gore3, S. Howard2, J. Pommier2, T. Bates4, P. Quinn4, D. A. Chu5, Bo-Cai Gao6, E. Fetzer7, W. McMillan8, S. Wetzel Seeman9, E. Borbas9
- 1SRI International, Menlo Park, CA USA, 2Bay Area Environmental Research Institute, Sonoma, CA USA, 3NASA Ames Research Center, Moffett Field, CA USA, 4NOAA PMEL, Seattle, WA USA, 5NOAA Goddard Space Flight Center, Greenbelt, MD USA,
- 6Naval Research Laboratory, Washington, DC USA, 7Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA, 8University of Maryland Baltimore County, Baltimore, MD USA, 9University of Wisconsin – Madison, CIMSS, Madison, WI USA

**Abstract**

- The NASA Ames 14-channel Airborne Tracking Sunphotometer (AATS-14) took measurements from aboard a Jetstream 31 (J31) twin turboprop aircraft during 19 science flights (~53 flight hours) over the Gulf of Maine during 12 July – 8 August 2004.  The flights were conducted in support of the INTEX-NA (INtercontinental chemical Transport EXperiment-North America) and ITCT (Intercontinental Transport and Chemical Transformation of anthropogenic pollution) field studies.  AATS-14 measures the solar direct-beam transmission at 14 discrete wavelengths between 354 and 2138 nm, and provides instantaneous measurements of aerosol optical depth (AOD) at 13 wavelengths and water vapor column content, which is derived from measurements at 940 nm and surrounding wavelengths.  AATS-14 measurements obtained during aircraft ascents and descents are differentiated to yield vertical profiles of aerosol extinction and water vapor density.
- Specific J31 flight patterns were designed to address a variety of science goals and, therefore, included a mixture of vertical profiles (spiral and ramped ascents and descents) and constant altitude horizontal transects at a variety of altitudes.  In general, flights were designed to include a near sea surface horizontal transect in a region of minimal cloud cover during or near the time of an Aqua and/or Terra satellite overpass, in addition to a low altitude flyby and vertical profile above the NOAA ship Ronald H. Brown.  In this paper, we compare AATS-14 water vapor profiles with simultaneous measurements obtained with a Vaisala humidity sensor on board the J31 and with spatially and temporally near-coincident data from radiosondes launched from the Ron Brown.  AATS-14 water vapor retrievals are also compared with retrievals from measurements acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on Aqua and Terra and by AIRS (Atmospheric Infrared Sounder) on Aqua during near-coincident satellite overflights.

- Funding for this research has been provided by the NOAA Atmospheric Chemistry and Climate Program, the NASA Tropospheric Chemistry Program, the NASA Radiation Sciences Program, and the NASA Earth Observing System Inter-Disciplinary Sciences (EOS-IDS) Program.

**AATS-14, J31 Vaisala, and MODIS Retrieval Comparisons**

**AIRS Retrieval Comparisons**

**AATS-14 and J31 Vaisala Retrieval Comparisons during J31 Vertical Profiles**

**Airborne, balloonsonde, and satellite water vapor retrievals are presented for four MODIS overflights.  Left frames: temporal plots of J31 altitude and AATS-14 retrievals of columnar water vapor (CWV, g/cm****2**** or precipitable cm) above aircraft altitude.  Middle left frames: profiles of CWV and water vapor density derived from measurements made by AATS-14, J31 Vaisala humidity sensor, and Vaisala balloonsonde launched from NOAA Ship Ronald H. Brown.  Middle right frames: color-coded maps of MODIS infrared full column water vapor retrievals, complete J31 flight track overlay (dashed line), and corresponding color-coded AATS-14 CWV above aircraft altitude for J31 flight altitudes at or below 100 m ASL.  Right frames: scatterplots of MODIS-vs.-AATS CWV and MODIS-minus-AATS CWV differences vs. AATS CWV; no estimate of the amount of water vapor in the layer between the sea surface and the J31 has been added to the AATS retrievals.**

**AATS-14 retrievals and J31 Vaisala measurements are overplotted with temporally and spatially near-coincident water vapor density retrievals from the Atmospheric Infrared Sounder (AIRS) during three Aqua overflights.  Left: J31 flight tracks color-coded according to aircraft altitude; location of AIRS grid centers (colored upward-pointing triangles) where water vapor profiles have been retrieved at standard atmosphere pressure surfaces.  Right: overlays of AIRS water vapor density profile retrievals (colored upward-pointing triangles connected by dashed lines for ease in viewing) at the locations shown in the adjacent map and corresponding water vapor density retrievals from AATS-14 and J31 Vaisala measurements during the J31 ascent or descent nearest in time and space to the AIRS retrievals.**

**Detailed comparisons (top three multi-frame plots) of AATS-14 retrievals of columnar water vapor or water vapor density and coincident J31 Vaisala humidity sensor measurements are shown for 33 separate J31 vertical profiles.  Results for all 33 cases are summarized in AATS-vs.-Vaisala scatterplots: (Bottom left) the amount of water vapor in the layer between the lowest and highest aircraft altitudes for a particular profile, (Bottom middle) water vapor density at all altitudes, and (Bottom right) water vapor density at altitudes below 3 km.**

**21 July**

**29 July**

**02 Aug**

**08 Aug**

**Aqua MODIS overpass time**