Rain Formation and Discharge nearby Coastlines, as observed by TRMM Reuven H. Heiblum, Ilan Koran, Orit Altaratz Department of Environmental Sciences and Energy Research, Weizmann Institute of Science. כנס שנתי אמ " י

Motivation 1998 – 2011 Winter Seasons (November – March).

Previous Studies (Neumann 1951) (Noppel et al. 2010) Many others, such as: 2D Numerical Model by Khain et al. 1993, Observations by Kutiel and Sharon 1980, Altaratz et al. 2001, Levin et al

WARM COOL L Land Breeze Synoptic

Objectives 1.Classification of the coastal rain band. 2.Separation of breeze dynamical effects and orographic forcing. 3.Test breeze theory in context of the intra- seasonal and diurnal variability.

Methods TRMM – Tropical Rainfall Measurement Mission. 36  N - 36  S. Non Sun-Synchronous orbit. TRMM 2B31 product: Combination of radar and microwave imager. IHM: Integrated Hydrometeor Mass [kg/m²], correlated with surface rain rates (R²=0.8). Main Limitations: 1. Insensitive to RR<0.7mm/hr. 2. Weaker performance over steep topography. Taken from:

Regions of Interest Intra-Seasonal Division: Alpert et al. 1990, Goldreich et al. 2004, Goldreich Autumnal Winter: November-December 2.Deep Vortices Winter: January-March

Results: Entire Region 50% of intra-seasonal IHM decrease due to colder atmosphere Most of strong precipitation is formed offshore!

Orographic gaussian located km before ridge peak (max elevation gradient). Breeze:Orographic gaussian amplitude ratio changes from 2:1 during Nov-Dec to 1:2 during Jan-Mar. Results: Lebanon

Orographic gaussians much wider during Jan-Mar. Gaussians’ amplitude ratio changes from 5:2:4 during Nov-Dec to 3:5:3 during Jan-Mar. Results: Israel

Results: Diurnal Variations Max Land Breeze

Other Regions… breeze wind

Conclusions Near coastline dynamics have a major effect on precipitation formation and discharge in the Eastern Mediterranean. Breeze dynamics dominates Nov-Dec. For Jan-Mar, orographic forcing dominates the distributions. Rain harvesting over sea (Levin et al. 2004) or rain delay by aerosol seeding (Noppel et al. 2010) may be very beneficial to the regional water budget.