Diagnosis of tropospheric moisture over Saudi Arabia and influences of IOD and ENSO

• Published in: Monthly weather review Vol. 134; no. 2; pp. 598 - 617
• Main Authors: CHAKRABORTY, Arun, BEHERA, Swadhin K, MUJUMDAR, Milind, OHBA, Ryohji, YAMAGATA, Toshio
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.02.2006
• Subjects: Arid zones; Atmospheric circulation; Atmospheric research; Climatology; Correlation analysis; Correlation coefficient; Earth, ocean, space; El Nino; Exact sciences and technology; External geophysics; Fluctuations; Marine; Meteorology; Moisture; Precipitation; Seasonal variations; Semiarid lands; Summer; Troposphere; Water content; Water in the atmosphere (humidity, clouds, evaporation, precipitation); Saudi Arabia; Arabian Peninsula; ISW, Arabian Sea, Persian Gulf; ISW, Indian Ocean; ISW, Red Sea; ISW, Saudi Arabia; atmospheric precipitation; sensitivity analysis; ocean-atmosphere interaction; troposphere; Interannual variation; El Nino; Arid region; Asia; Semi arid zone; Southern oscillation; Precipitable water; seasonal variations; Atmospheric humidity
• ISSN: 0027-0644; 1520-0493
• DOI: 10.1175/mwr3085.1

A diagnostic study of atmospheric moisture data over Saudi Arabia derived from a 43-yr National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis revealed that moisture convergence in the lower troposphere and divergence in and above the middle troposphere occurs throughout the year. Although the amount of precipitable water content in the middle troposphere is high, precipitation is less than expected over this semiarid region during a boreal summer monsoon season because of strong moisture divergence. The net tropospheric moisture flux over the arid and semiarid regions of Saudi Arabia shows seasonal and interannual variability. The seasonal variability has a strong semiannual signal with its primary peak February-April and its secondary peak June-August. This pattern is consistent with a similar semiannual signal observed in rainfall climatology. The restricted moisture supply to southwestern Saudi Arabia during summer presumably explains the lack of precipitation in other areas of the country. Winter precipitation, however, is widespread. The increased transport of net atmospheric moisture flux is higher during El Nino and positive Indian Ocean dipole (IOD) phenomena. During these events, influx across the Red Sea (west) side of Saudi Arabia increases. The net flux to the region is reduced by a slight increase of outflux across the Persian Gulf (east) side. Reanalysis data and model-sensitivity experiments show that El Nino or a concurrent positive IOD and El Nino event more strongly amplify net transport than does an independent positive IOD event. The partial-lag correlation analysis with net moisture flux from the Red Sea side shows that the positive IOD mode has a peak correlation coefficient of 60.5 with close to a 5-month lead and that El Nino has a peak correlation coefficient of 60.6 with close to a 2-month lead.