Convective rain cells: Radar‐derived spatiotemporal characteristics and synoptic patterns over the eastern Mediterranean

Abstract

[1] This paper examines the spatiotemporal characteristics of convective rain cells over the eastern Mediterranean (northern Israel) and their relationship to synoptic patterns. Information on rain cell features was extracted from high-resolution weather radar data. The radar-gauge adjustment, validation, cell segmentation and tracking techniques are discussed at length at the beginning of the paper. Convective rain cells were clustered into three synoptic types (two winter lows-deep Cyprus lows and shallow lows-and one tropical intrusion, Active Red Sea Trough) using several NCEP/NCAR parameters, and empirical distributions were computed for their spatial and temporal features. In the study region, it was found that the Active Red Sea Trough rain cells are larger, live for less time and possess lower rain intensities than the rain cells generated by the winter lows. The Cyprus low rain cells were found to be less intense and slightly larger on average than the shallow low rain cells. It was further discovered that the preferential orientation of the rain cells is associated with the direction and velocity of the wind. The effect of distance from the coastline was also examined. An increase in the number and area of the rain cells near the coastline was observed, presumably due to the sea breeze convection. The mean rainfall intensity was found to peak near the shore and decrease with distance inland. This information is of great importance for understanding rain patterns and can be further applied in exploring the hydrological responses of the basins in this region.Citation: Peleg, N., and E. Morin (2012), Convective rain cells: Radar-derived spatiotemporal characteristics and synoptic patterns over the eastern Mediterranean,

A framework for assessing hydrological regime sensitivity to climate change in a convective rainfall environment: a case study of two medium-sized eastern Mediterranean catchments, Israel

“…The synoptic classification during these periods was performed using a cluster analysis technique that considers four variables from the reanalysis data: (1) sea level pressure, (2) specific humidity at 700 hPa, (3) geopotential height at 500 hPa; and (4) zonal wind at 850 hPa. Initially, three wet synoptic systems classes were identified (Peleg and Morin, 2012). However, the first two were merged into one synoptic class -known as the Mediterranean low (ML), an extratropical cyclone, see Fig.…”

“…1). The ML is the prevailing synoptic system that generates rainfall over the study region (Alpert et al, 2004;Peleg and Morin, 2012;Saaroni et al, 2010). The second synoptic system ( Fig.…”

“…To achieve this goal the following methods and models (Fig. 1, left side in italic) were used: (1) a synoptic classification was carried out using the NCEP/NCAR reanalysis data (Peleg and Morin, 2012); (2) convective rainfall space-time characterization and the associated empirical distributions per synoptic system were computed using data (Peleg and Morin, 2012;Peleg et al, 2013); (3) selected GCM simulations from CMIP5 were bias corrected and changes in the occurrence frequency of the synoptic systems between the historical and future periods were estimated ; (4) rainfall ensembles with convective features for current and projected climate were generated by the HiReS-WG ; and (5) the streamflow in the catchments' outlets was simulated using the Sacramento Soil Moisture Accounting Model (SAC-SMA) (Shamir et al, 2014a).…”

Probing the precipitation life cycle by iterative rain cell tracking

“…[4] Various objective tracking methods have been developed and advanced during the last 2 decades, mainly for the purpose of nowcasting strong convective events like thunderstorms [Rosenfeld, 1987;Dixon and Wiener, 1993;Wilson et al, 1998;Johnson et al, 1998;Handwerker, 2002;Hering et al, 2005;Novo et al, 2013] but also the mean life cycles of the cell size and statistics of tracked rain cells have been studied [Kysnarova and Novak, 2009;Peleg and Morin, 2012;Rigo et al, 2012]. Other tracking methods have been applied not only to radar data but also to other high-resolution observational data sets such as satellite data [Lakshmanan et al, 2009;Feng et al, 2012].…”

“…Some classification methods utilize the detection of a stratiform "bright band" in radar reflectivity [Steiner et al, 1995;Smyth and Illingworth, 1998;Houze Jr., 1997], observed intensity distributions [Llasat, 2001], or cluster analysis [Peleg and Morin, 2012], allowing the identification of even more than two classes. For our study, we use a methodology based on human synoptic cloud observations, previously employed to distinguish the two precipitation types [Berg et al, 2013].…”