Itamar M. Lensky

Satellite-Based Insights into Precipitation Formation Processes in Continental and Maritime Convective Clouds

Multispectral analyses of satellite images are used to calculate the evolution of the effective radius of convective cloud particles with temperature, and to infer from that information about precipitation forming processes in the clouds. Different microphysical processes are identified at different heights. From cloud base to top, the microphysical classification includes zones of diffusional droplet growth, coalescence droplet growth, rainout, mixed-phase precipitation, and glaciation. Not all zones need appear in a given cloud system. Application to maritime clouds shows, from base to top, zones of coalescence, rainout, a shallow mixed-phase region, and glaciation starting at −10°C or even warmer. In contrast, continental clouds have a deep diffusional growth zone above their bases, followed by coalescence and mixed-phase zones, and glaciation at −15° to −20°C. Highly continental clouds have a narrow or no coalescence zone, a deep mixed-phase zone, and glaciation occurring between −20° and −30°C. Limit...

Estimation of Precipitation Area and Rain Intensity Based on the Microphysical Properties Retrieved from NOAA AVHRR Data

Abstract This paper investigates the feasibility of a quantitative estimation of precipitation from space, based on retrieval of microphysical properties of cloud tops using Advanced Very High Resolution Radiometer data. The effective radius re of cloud particles is calculated for highly reflective clouds in the visible wavelength, assuming that these are water clouds with infinite optical thickness at the 3.7-μm channel. A large effective radius indicates the presence of large droplets and/or ice in the clouds. The distinction between large droplets and ice is not necessary because the existence of either near the tops of thick clouds is conducive to the precipitation formation processes. In addition to the microphysical information, the fraction of rain cloud coverage and cloud spatial structure (convective and stratiform) were used for the rain estimation algorithm. The satellite estimates were compared to radar data. Encouraging results were obtained for winter precipitation clouds in Israel with a wi...

A Night-Rain Delineation Algorithm for Infrared Satellite Data Based on Microphysical Considerations

Abstract Information about the microstructure and precipitation potential of cloud revealed by the brightness temperature difference between a thermal IR channel (11 μm) and a mid-IR channel (3.7 μm) at nighttime is implemented into a precipitation delineation algorithm. The algorithm is simple to implement and uses data available from almost all of the operational and research satellites. The delineation algorithm performs well also in cases of warm clouds over land for which passive microwave algorithms fail.

Satellite-Based Insights into Precipitation Formation Processes in Continental and Maritime Convective Clouds at Nighttime

Abstract Nighttime microphysical retrievals can be obtained to a much lesser accuracy than those of the daytime, because of lack of the solar radiation. However, a proper treatment of the brightness temperature difference (BTD) between a thermal IR channel (11 μm) and a mid-IR channel (3.7 μm) reveals information about the microstructure and precipitation potential of clouds at nighttime. The two factors that contribute to large BTD are the particle size at cloud top and the optical depth of the cloud layer. These two factors have contradictory effects on precipitation. The respective contributions were simulated and compared with observations of the Tropical Rainfall Measuring Mission. Based on that, a method was developed to use the distribution of BTD with cloud-top temperature for retrieving cloud microstructure and precipitation properties.

Demographic and environmental risk factors for infection by Theileria equi in 590 horses in Israel.

The prevalence of Theileria equi infection as well as the environmental and demographic risk factors for infection was studied in 590 healthy horses from 46 farms in Israel. The prevalence of T. equi DNA was assessed using a polymerase chain reaction for a segment of the Theileria 18S rRNA gene. The overall prevalence was 26.4% (156/590). There was a significant geographical variation in the prevalence of T. equi infection, ranging from 9.3% (25/270) in the central lowlands to 81.7% (49/60) in the Golan Heights. The prevalence of T. equi infection was found to be significantly associated with management types with more horses with access to pasture being positive. Breed was identified as a risk factor for T. equi infection in a univariate analysis with relatively high infection rates in the Quarter horse and local breeds (41.1% and 36.3% respectively), while ponies and Arabian horses had a relatively low prevalence (10% and 9.1%, respectively). However, since a correlation between geographic location and breed was found, it is difficult to draw definite conclusions regarding this risk factor. Age and gender were not found as risk factors for T. equi infection in this study. The environmental variables that were significantly associated with positivity were relative humidity and minimum land surface temperature at day which both showed negative correlation with T. equi prevalence. In conclusion, Israel was found to be enzootic for T. equi infection, as indicated by the high sub-clinical infection rate, which differed between geographical areas.

A Phenology-Based Method for Monitoring Woody and Herbaceous Vegetation in Mediterranean Forests from NDVI Time Series

We present an efficient method for monitoring woody (i.e., evergreen) and herbaceous (i.e., ephemeral) vegetation in Mediterranean forests at a sub pixel scale from Normalized Difference Vegetation Index (NDVI) time series derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). The method is based on the distinct development periods of those vegetation components. In the dry season, herbaceous vegetation is absent or completely dry in Mediterranean forests. Thus the mean NDVI in the dry season was attributed to the woody vegetation (NDVIW). A constant NDVI value was assumed for soil background during this period. In the wet season, changes in NDVI were attributed to the development of ephemeral herbaceous vegetation in the forest floor and its maximum value to the peak green cover (NDVIH). NDVIW and NDVIH agreed well with field estimates of leaf area index and fraction of vegetation cover in two differently structured Mediterranean forests. To further assess the method’s assumptions, understory NDVI was retrieved form MODIS Bidirectional Reflectance Distribution Function (BRDF) data and compared with NDVIH. After calibration, leaf area index and woody and herbaceous vegetation covers were assessed for those forests. Applicability for pre- and post-fire monitoring is presented as a potential use of this method for forest management in Mediterranean-climate regions.

Prevalence of the symbiont Cardinium in Culicoides (Diptera: Ceratopogonidae) vector species is associated with land surface temperature

Prevalence of infection by bacterial symbionts may reflect their interactions with the host and has been shown to be correlated with environmental factors. Yet, it is still unclear whether infection by symbionts is determined by environmental factors affecting the early or imago stage of the host. Here, we identified and localized the symbiont Candidatus Cardinium hertigii (Bacteroidetes) in sympatric Culicoides biting midge species, examined its abundance, and studied its association with environmental factors. The prevalence of adult infection differed, with 50.7% from C. imicola, 31.4% from C. oxystoma, and 0% from C. schultzei gp., although phylogenetic analyses showed that Cardinium in these species is almost identical. In addition, prevalence of infection differed between climate regions, with lowest prevalence in the arid region and highest prevalence in the Mediterranean region. Multivariate linear regression analysis of Cardinium prevalence together with climatic and satellite imagery data‐derived environmental variables revealed that infection prevalence is significantly associated with land surface temperature and explained up to 89.7% of infection prevalence variability. These findings suggest that the observed variation of Cardinium infection of the imago stage of Culicoides may be influenced by environmental conditions during the latters early developmental stages.—Morag, N., Klement, E., Saroya, Y., Lensky, I., Gottlieb, Y. Prevalence of the symbiont Cardinium in Culicoides (Diptera: Ceratopogonidae) vector species is associated with land surface temperature. FASEB J. 26, 4025–4034 (2012). www.fasebj.org

A Satellite-Based Parameter to Monitor the Aerosol Impact on Convective Clouds

Abstract A method to monitor the aerosol impact on convective clouds using satellite data is presented. The impacts of forest fires and highly polluting megacities on cloud precipitation formation processes are quantified by the vertical extent above cloud base to which convective cloud tops have to develop for onset of precipitation in terms of temperature difference D15. Large D15 is a manifestation of the precipitation suppression effect of small cloud condensation nuclei aerosols that elevate the altitude where effective precipitation processes are initiated. A warmer land surface with a greater sensible heat flux that increases the updraft velocity at cloud base may also contribute to the same effect. Therefore, D15 is greater for clouds that develop over more polluted and/or warmer surfaces that result from smoke and urban pollution and/or urban heat island, respectively. The precipitation suppression effects of both smoke from forest fires and urban effects can be vividly seen in a case study over ...

The Effect of Planting Techniques on Arid Ecosystems in the Northern Negev

Forestation is a widely accepted way to combat desertification. This approach can have tremendous beneficial effects on soil and environment. The United Nations Food and Agriculture Organization recommended Acacia victoriae for rehabilitation of degraded arid environments. For that purpose areas in the Northern Negev were planted with Acacia victoriae in the period of 1990–1993. The planting techniques were: sparse plantings (Contour trenching and Savanna), and dense planting of woodland. We divided each of those treatments into planted and control plots. In the plots planted by contour trenching the values of annual biomass per area, nutrient and Soil Organic Carbon (SOC) contents underneath the trees canopies were the lowest, while those values in the planted savanna and woodland plots were significantly higher. Contour trenching also harmed the soil by causing erosion, and decreasing the soils water holding capacity. Therefore, Woodland and Savanna plantings should be preferred over contour trenching in arid areas.

High relative abundance of the stable fly Stomoxys calcitrans is associated with lumpy skin disease outbreaks in Israeli dairy farms

The vector of lumpy skin disease (LSD), a viral disease affecting Bovidae, is currently unknown. To evaluate the possible vector of LSD virus (LSDV) under field conditions, a yearlong trapping of dipterans was conducted in dairy farms that had been affected by LSD, 1‐2 years previously. This was done in order to calculate monthly relative abundances of each dipteran in each farm throughout the year. The relative abundances of Stomoxys calcitrans (Diptera: Muscidae) in the months parallel to the outbreaks (December and April) were significantly higher than those of other dipterans. A stable fly population model based on weather parameters for the affected area was used to validate these findings. Its results were significantly correlated with S. calcitrans abundance. This model, based on weather parameters during the epidemic years showed that S. calcitrans populations peaked in the months of LSD onset in the studied farms. These observations and model predictions revealed a lower abundance of stable flies during October and November, when LSD affected adjacent grazing beef herds. These findings therefore suggest that S. calcitrans is a potential vector of LSD in dairy farms and that another vector is probably involved in LSDV transmission in grazing herds. These findings should be followed up with vector competence studies.