Showing papers by "Pinhas Alpert published in 2011"

Extreme value indicators in highly resolved climate change simulations for the Jordan River area

Abstract: [1] Understanding changing trends and frequency of extreme rainfall and temperature events is extremely important for optimal planning in many sectors, including agriculture, water resource management, health, and even economics. For people living in the Jordan River region of the Middle East such changes can have immediate devastating impacts as water resources are already scarce and overexploited and summer temperatures in the desert regions can reach 45°C or higher. Understanding shifts in frequency and intensity of extreme events can provide crucial information for planning and adaptation. In this paper we present results from regional climate model simulations with RegCM3 and MM5 centered on the eastern Mediterranean region. Our analysis focuses on changes in extreme temperature and rainfall events. We show that maximum daily summer temperature is expected to increase by between 2.5°C and 3°C, with an increase in warm spell length. Precipitation extremes are expected to increase with longer dry spells, shorter wet spells, and increases in heavy rainfall. Model agreement for the control period 1961–1990 is higher in the southern region than in the north, perhaps because of the complex topography, suggesting that even small differences in spatial scale play an important role. In addition, we notice that the chosen global model plays an important role in determining future temperature trends, while the choice of regional climate model is critical for understanding how precipitation is expected to evolve.

A double-resolution transient RCM climate change simulation experiment for near-coastal eastern zone of the Eastern Mediterranean region

Abstract: A double-resolution regional experiment on hydrodynamic simulation of climate over the eastern Mediterranean (EM) region was performed using an International Center for Theoretical Physics, Trieste RegCM3 model. The RegCM3 was driven from the lateral boundaries by the data from the ECHAM5/MPI-OM global climate simulation performed at the MPI-M, Hamburg and based on the A1B IPCC scenario of greenhouse gases emission. Two simulation runs for the time period 1960-2060, employing spatial resolutions of 50 km/14 L and 25 km/18 L, are realized. Time variations of the differences in the space distributions of simulated climate parameters are analyzed to evaluate the role of smaller scale effects. Both least-square linear and non-linear trends of several characteristics of the EM climate are evaluated in the study. One of the key findings with regard to linear trends is a notable and statistically significant precipitation drop over the near coastal EM zone during December-February and September-November. Statistically significant positive air temperature trends are projected over the entire EM region during the four seasons. Also projected are increases in air temperature extremes and the relative contribution of convective processes in the Southern Mediterranean coastal zone (ECM) region. A notable sensitivity of projected larger-scale climate change signals to smaller-scale effects is also demonstrated.

Aerosol optical thickness trends and population growth in the Indian subcontinent

Abstract: The Indian subcontinent occupies 2.4% of the world land mass and is home to ∼17% of the world population. It is characterized by a wide range of population density P, significant population growth and high levels of air pollution. The quantification of the effect of urbanization on aerosol optical thickness AOT trends was carried out by analysing 8-year March 2000 to February 2008 Moderate Resolution Imaging Spectroradiometer MODIS and Multiangle Imaging SpectroRadiometer MISR satellite data. Here we show that over extensive areas with differing population densities, which are significant parts of the Indian subcontinent, 1 the higher the averaged population density the bigger the averaged AOT and 2 the larger the population growth the stronger the increasing trends in AOT. Over the regions with P > 100 persons km−2 more than 70% of the territory, a population growth of ∼1.5% year−1 was accompanied by increasing AOT trends of over 2% year−1. The presence of the aforementioned AOT trends is evidence of air quality deterioration, in particular in highly populated areas with P > 500 persons km−2. This situation could worsen with the continued growth of the Indian population.

Regional and local climatic effects on the Dead-Sea evaporation

Abstract: The natural evaporation in the Dead-Sea is a very important meteorological parameter to the local industries at Sdom. It was found that the pan evaporation in Sdom has recently increased by 20–25%. In this paper we explore the reasons for this increase. It is found that both large-scale and local climatic changes have contributed to the evaporation increase in the Dead Sea Valley. The large-scale (global) change potentially associated with the global warming, resulted in changes of the frequencies of some synoptic systems in the region. The local change is a result of the recent Dead-Sea drying, which reduced the local Dead-Sea breeze while intensifying the Mediterranean-Sea breeze penetrating the Dead Sea Valley. It is suggested that while the local effect was the dominant climatic change factor in the Dead-Sea Valley in the 1970–1990, the global effect becomes the dominant one in the more recent evaporation increase in the Dead-Sea.

Climatological relationships among the moisture budget components and rainfall amounts over the Mediterranean based on a super‐high‐resolution climate model

Abstract: [1] Moisture budget components over a rectangular region defined by the longitudes 6.0°W–36.0°E and latitudes 30.0°N to 45.0°N, with an area of about 6.08 × 106 km2 over the Mediterranean (Med) Basin, are studied by the use of the Japan Meteorological Agency super-high-resolution (20 km) GCM monthly mean data. The research time periods are 1979–2007 for current run and 2075–2099 for future run. Six rainy months of October to March with a total of 168 months for the current run and 144 months for the future run were selected. The rain months have been categorized into five groups of months based on the mean monthly rainfall amounts where the five groups are P < 1.0, 1.0 ≤ P < 1.5, 1.5 ≤ P < 2.0, 2.0 ≤ P < 2.5, and 2.5 mm/d ≤ P. We found that generally, over the Mediterranean, the outflow-inflow is balancing the independently calculated evaporation-precipitation quite well with a correlation coefficient of about 0.89. The present seasonal (October-March) precipitation simulated from the 20 km GCM showed a quite reasonable agreement with the CRU. The seasonal area mean precipitation and evaporation are 1.85 mm/d and 2.44 mm/d, respectively. The largest two precipitation categories contribute over 50% of the total seasonal rainfall. The evaporation varies positively with the precipitation for all precipitation categories. Also, the relatively high mean recycling ratio (55%) indicates that the local Med evaporation has a central role in the local precipitation. Another important finding is that the decreasing trend of recycling ratio with the rising of the precipitation category implies that the outside moisture inflow role increases with the increase of the precipitation category. For all the precipitation categories, the total outflow is larger than the total inflow, indicating that the Med area is an important source of moisture. Individual boundary moisture flux shows that the main moisture comes from the west boundary and contributes 59% of the total inflow, while the main outflow is through east boundary and is responsible for 46% of total outflow. Analysis of monthly precipitation indicates that the October and November have the two largest amount of precipitation over the research region. The moisture budget study separated for the east and the west Med shows that the area mean precipitation for the east and the west Med are 2.14 and 2.29 mm/d, while the evaporation are 4.48 and 3.59 mm/d. The plausible reason for the differences between these two basins has been discussed. The moisture supplies to the east Med is mainly from the west boundary, while for the west Mediterranean, the north boundary inflow also plays an important role along with the west boundary. The future moisture budget components over Med suggest that the precipitation is decreasing from 1.85 to 1.62 mm/d and the evaporation is increasing from 2.44 to 2.56 mm/d between current and future. Another finding is that the largest precipitation number of months decreases from 12% to only 6% of the total number of months, while the intensity of the precipitation in this category enhances in the future.

Factor Separation in the Atmosphere: Applications and Future Prospects

Abstract: 1. Introduction Pinhas Alpert 2. The Factor Separation method and the fractional approach Pinhas Alpert and Tatiana Sholokhman 3. Investigation of the FS features for basic mathematical functions Pinhas Alpert and Tatiana Sholokhman 4. Factor Separation and paleoclimates Andre Berger, Martin Claussen and Qiuzhen Yin 5. Meso-meteorology: Factor Separation examples in atmospheric meso-scale motions Pinhas Alpert 6. Using the Factor Separation method for land-use land-cover change impacts on weather and climate process with the Regional Atmospheric Modeling System Adriana Beltran-Przekurat, Roger A. Piekle, Sr, Joseph L. Eastman, Gemma T. Narisma, A. J. Pitman, Ming Lei and Dev Niyogi 7. Application of Factor Separation to heavy rainfall and cyclogenesis: Mediterranean examples Romu Romero 8. Experience in applying Factor Separation analysis to assessing urban land-use and aerosol impacts on precipitation Susan C. van den Heever, Christopher M. Rozoff and William R. Cotton 9. Free and forced thermocline oscillations in Lake Tanganyika Olivier Gourgue, Eric Deleersnijder, Vincent Legat, Emmanuel Marchal and Laurent White 10. Application of the Factor Separation method to quantify the effect of waste heat, vapour and pollution on cumulus convection Gerhard W. Reuter 11. The use of Factor Separation method for climate variable interaction studies in hydrological land surface models and crop yield models Dev Niyogi, R. Mera, Yongkang Xue, G. Wilkerson and F. Booker 12. Linear model for the sea breeze Tatiana Sholokhman and Pinhas Alpert 13. Experience and conclusions from the Factor Separation method: ensemble data assimilation and forecasting applications Dorita Rostkier-Edelstein and Joshua P. Hacker 14. Tagging systematic errors arising from different components of dynamics and physics in forecast models T. N. Krishnamurti and Vinay Kumar 15. Some difficulties and prospects Pinhas Alpert and Tatiana Sholokhman 16. Summary Pinhas Alpert Index.

Humidity Measurements using Commercial Microwave Links

Abstract: Atmospheric humidity strongly affects the economy of nature and has a cardinal part in a variety of environmental processes (e.g. Allan et al., 1999). As the most influential of greenhouse gases, it absorbs long-wave terrestrial radiation. Through the water vapour evaporation and recondensation cycle, it plays a central part in the Earth's energy redistribution mechanism by transferring heat energy from the surface to the atmosphere. Meteorological decision-support for weather forecasting is based on atmospheric model results, the accuracy of which is determined by the quality of its initial conditions or forcing data. Humidity, in particular, is a critical variable in the initialization of these models. The Mesoscale Alpine Programme (MAP) which set out to improve prediction of the regional weather, and specifically rainfall and flooding, concluded that accurate moisture fields for initialization were of great importance in achieving improved results (Ducrocq et al., 2002). Humidity measurements are predominantly obtained by either surface stations, radiosondes or satellite systems. The typical surface station instruments commonly provide only very local, point, observations, and therefore suffer from low spatial resolution. Moisture though, is a field with an unusually high variability in the mesoscale as demonstrated, for instance, by structure functions (Lilly & Gal-Chen, 1983). Compounding this problem is the limited accessibility to position humidity gauges in heterogeneous terrain, or areas with complex topography. Satellites allow for a large area to be covered, but are frequently not accurate enough in measuring surface level moisture while this near-surface moisture is, in most cases, the important variable for convection. Radiosondes, which are typically launched only 2-4 times a day, also provide very limited information. Additionally, these monitoring methods are costly for implementation, deployment and maintenance. Because of surface perturbation a point measurement close to the surface (for example 2m from the ground as in a standard meteorological surface station) is not satisfactory for model initialization. What is ideally required for meteorological modeling purposes is an area average measurement of near-surface moisture over a box with the scale of the model's grid and at an altitude of a few tens of meters. Current measuring tools cannot effectively provide this type of data. The method we present in this chapter provides a unique way of obtaining precisely this type of measurement. We introduce a technique, originally published by David et al. (2009), to measure atmospheric humidity using data collected by wireless communication networks.

Sea-Salt Aerosol Forecasts Compared with Wave Height and Sea-Salt Measurements in the Open Sea

Abstract: Sea-salt aerosol (SSA) could influence the Earth’s weather and climate acting as cloud condensation nuclei. In spite of the importance of SSA effects on the Earth’s climate and weather, there were no measurements of sea-salt aerosols in the open sea. At Tel-Aviv University, the DREAM-Salt prediction system has been producing daily forecasts of 3-D distribution of sea-salt aerosol concentrations over the Mediterranean model domain 20 W–45E, 15 N–50 N (http://wind.tau.ac.il/salt-ina/salt.html). In order to evaluate the model performance in the open sea, daily modeled sea-salt aerosol concentrations were compared directly with sea-salt ground-based measurements taken at the tiny island of Lampedusa, in the Central Mediterranean. In order to further test the robustness of the model, the model performance over the open sea was indirectly verified by comparing modeled SSA concentrations with wave height measurements collected by the ODAS Italia 1 buoy. Model-vs.-measurement comparisons show that the model is capable of producing realistic SSA concentrations and their day-to-day variations over the open sea, in accordance with observed wave height and wind speed.

Improved CTM Boundary Conditions Using DREAM Desert Dust Forecasts: A Case Study over the Po Valley

Abstract: The Po Valley in Northern Italy is frequently affected by high PM10 concentrations, where both natural and anthropogenic sources play a significant role. This work was aimed at giving a proper account of the contribution of Saharan dust to air quality in the Po Valley. This was carried out by improving the boundary conditions of the mesoscale 3D deterministic Transport Chemical Aerosol Model (TCAM) on large-scale transport of Saharan dust, daily predicted over the Mediterranean region. A case study of the integration of the TCAM and DREAM models was implemented over the Po Valley. The results show that the use of improved boundary conditions leads TCAM to better performances, both in terms of correlation and mean errors: TCAM was able to more accurately reproduce high PM10 concentrations observed in the Po Valley during particular dust events.