Hadas Saaroni

Outdoor comfort research issues

The paper discusses methodological issues and carrying out problems in outdoor comfort research. It also deals with the relative effects of air temperature, solar radiation and wind speed, as well as with the relationship between thermal sensation and overall comfort sensation, as was found in the outdoor comfort research in Japan. The paper also summarizes several studies going on presently at Tel Aviv University in Israel and presents some of the actual experimental results from these studies.

Spatial distribution and microscale characteristics of the urban heat island in Tel-Aviv, Israel

Abstract A significant urban heat island (UHI) was identified in Tel-Aviv on a stable winter day. The UHI detection was performed using air temperatures at both the roof and the street levels (using fixed-station and car-traverse measurements) and at the surface level (using an airborne thermal video radiometer [TVR]). Whereas the complex microscale characteristics of the UHI studied by the TVR at the surface level showed variations of up to 10°C, at the street level, air temperature variations of 3–5°C were identified between the city center and the surrounding areas. It was found that during the nighttime, the warm Mediterranean Sea has a moderating effect on the roof-level temperatures, whereas, at the street level, the urban heat island is more pronounced. The combined method of monitoring the UHI from different levels and on different scales for the first time enabled a spatial assessment of the city’s UHI and its diverse thermal coverage characteristics. The thermal differences of neighborhoods, urban activity and urban components were compared. It was demonstrated that the city cover plays an important role in the thermal activity of Tel-Aviv. A similar UHI spatial pattern was obtained using isotherm maps, generated from the air temperatures at street level, and thermal images, generated by the TVR at the surface level. It was concluded that there are differences in the magnitude of the UHI at different levels of the canopy layer and at different times, but the UHI pattern has similar trends.

Chapter 2 Relations between climate variability in the Mediterranean region and the tropics: ENSO, South Asian and African monsoons, hurricanes and Saharan dust

Publisher Summary The Mediterranean climate is affected by several tropical and subtropical systems as illustrated by some evidence presented in this chapter. These factors range from the El Nino Southern Oscillation (ENSO) and tropical hurricanes to the South Asian Monsoon and Saharan dust. This leads to complex features in the Mediterranean climate variability. It reviews some tropical and subtropical teleconnections to the Mediterranean climate. It discusses the South Asian Monsoon (SAM), which is a key factor influencing the climate of the eastern and central Mediterranean. It causes high variability in sea level pressure (SLP) over Arabia and the Middle East with high pressures in winter and low pressures in summer. The adjustment to the SAM couples the falling pressure and land temperature over the Indian subcontinent/Asia Minor with rising pressure and temperature over the Persian Gulf and Iraq. Red Sea Trough intrusions into the Eastern Mediterranean and the Saharan dust are also discussed in the chapter.

Climate of the Mediterranean: synoptic patterns, temperature, precipitation, winds and their extremes

This chapter considers a set of issues related to the synoptic climatology of the Mediterranean region (MR). The main Northern Hemisphere teleconnections affecting the MR and their role on temperature, precipitation, and atmospheric cyclones are described. The characteristics of the cyclones in the MR are presented. The role of teleconnections and atmospheric regimes on temperature and precipitation is discussed. The content includes extremes of temperature, precipitation, wind, and storminess (considering also marine aspects such as waves and storm surges).

Summer rain episodes in a Mediterranean climate, the case of Israel: climatological–dynamical analysis

Summer in the eastern Mediterranean basin and the Levant region is characterized by an absence of rain. A persistent subsidence aloft, combined with a lower-level cool marine flow, results in a semi permanent inversion which suppresses vertical growth of low clouds, hence inhibiting rain production. However, rain episodes are observed over the northern half of Israel almost every year. This paper examines the regime of summer rainfall in Israel, based on measurements taken over the past 50 years. The rain episodes are found to be rather mild, producing only several millimetres of rainfall, each episode with a mode duration of 1 day. The rain is highly localized. The synoptic conditions during rain episodes are studied from the European Centre of Medium Weather Forecasting (ECMWF) data sets. These show that the prevailing summer synoptic system over the region remains unchanged during rain episodes, that the synoptic-scale subsidence exists throughout, but that the prevailing upper-inversion rises, weakens or even collapses as a result of cooling in the lower-mid-levels, presumably due to the enhanced cold advection within these levels. These findings, together with the observed locality of the rain, suggest that the cause of rain is not a synoptic-scale forcing, but rather a weakening of the rain-suppressive thermodynamic conditions over the Levant region. Copyright

Large-Scale Atmospheric Circulation Driving Extreme Climate Events in the Mediterranean and its Related Impacts

It is widely accepted that the Mediterranean basin represents one of the most prominent hot spots of climate change and is a particularly vulnerable region in the world. Recent trends toward a hotter and drier climate appear to be related to changes in atmospheric circulation patterns, particularly over the western Mediterranean. The combined effects of precipitation decrease and surface-temperature increase in the Mediterranean will most probably lead to important changes in the region’s water cycle. In fact, the present tendency toward a drier climate with a higher frequency of drought events agrees with climate change scenarios that point to increasing probabilities of drought episodes and severe heat waves (HWs). Here, we provide a multidisciplinary review of the state-of-the-knowledge science of these two natural hazards in the Mediterranean. This chapter covers a wide range of atmospheric circulation phenomena with a direct impact on climate and socioeconomic activities in the twentieth century and with relatively high probabilities of changing significantly throughout the twenty-first century (e.g., water resources, renewable energy, agriculture, and vegetation dynamics) and also natural hazards (e.g., droughts, HWs, and sea surges and flooding in Venice).

Trends in Daily Rainfall Intensity Over Israel 1950/1-2003/4

The study focuses on long-term trends of daily rainfall in Israel as a function of their intensity in order to identify potential trends in rainfall extremity. The study period is the rainy season, October-May between 1950/1 and 2003/4. For the total rainfall, an increased trend is shown across Israel, especially for the central and southern regions, though non-significant. Daily rainfall intensity showed non-significant trends of increase in the heavy rainfall at the center and south and decrease at the north. The light to moderate rainfall trends increased in the north while they decreased at the center and south. Trends are significantly correlated with known teleconnection patterns, especially the East Atlantic- Western Russia and the North Sea-Caspian Sea patterns. Positive trends toward heavier rainfall are noted in Israel, which are significant in several specific locations. This finding has to be carefully followed since the region is a climatic border subjected to severe water shortage and is predicted to dry-up in most global warming scenarios. During the last decades there is an increasing evidence for more extreme rainfall at different places around the globe. Global warming was suggested to be linked with an increase in heavy rainfall due to an increase in atmospheric vapor and the warmer air. This trend is shown in the 4 th Assessment Report of the IPCC (1). In general, the Mediterranean Basin shows decreasing trends in the precipitation amount (2-4). The EM shows mixed rainfall trends but almost all stations show a decreasing trend in the precipitation which is especially large and significant during winter in the Greek, Cypriot and Turkish stations (5). Precipitation reduction over most Greek stations, combined with enhanced anticyclonic activity over almost the whole Mediterranean was found during the late 1980s and the early 1990s, a period characterized by high North Atlantic oscillation index values (6). Time series of extreme precipitation cases in Greece for the period 1970-2002, did not reveal significant positive or negative trend (7). Alpert et al. (8) showed the paradoxical increase of Mediterranean extreme daily rainfall in spite of the decrease in the total rainfall. They showed an increase in the torrential rainfall in Italy and Spain, heavy rainfall in Israel and heavy- torrential rainfall over Cyprus for the period 1951-1995. These trends were significant only in Italy and Spain. Kostopoulou and Jones (5) analyzed seasonal and annual trends over the central and Eastern Mediterranean (EM, 1958-2000). They showed statistically significant positive trends toward intense rainfall events and greater amount of precipitation for stations around the Italian Peninsula. For the EM, i.e., the Balkan Peninsula, western Turkey and

Estimating the Urban Heat Island Contribution to Urban and Rural Air Temperature Differences over Complex Terrain: Application to an Arid City

Abstract This study proposes a method for estimating the canopy-layer net urban heat island (UHI) in regions with complex terrain that lack preurban observations. The approach is based on a linear relationship between the urban–rural temperature difference (ΔTu−r), measured via screen-level air temperature, and the population of the city, which was found to have the highest correlation with observations. The linear relation is extrapolated to zero population to yield the desired preurban value. The difference between the zero population ΔTu−r and the current one is proposed to represent the net UHI. Given the uncertainties of the population method, the relatively short time period of the temperature record, and possible inhomogeneity in the data, the results should be regarded as a first-order approximation of the net UHI contribution. The UHI was evaluated for an arid city, Beer Sheba, Israel, for the minimum and maximum air temperatures for the summer and the winter. The study region resembles the combi...

Human-biometeorological conditions and thermal perception in a Mediterranean coastal park.

This study looks at the interrelation of human-biometeorological conditions, physiological thermal stress and subjective thermal perception in the design and use of a new waterfront park in Tel-Aviv, Israel. Our initial assumption was that the parks design would embody a comprehensive response to the areas ever-increasing heat stress and water shortage. However, almost half of it is covered by grass lawns, irrigated with fresh water, while the remaining area is mainly covered with concrete paving, with minimal shading and sparse trees. We hypothesized that stressful thermal conditions would prevail in the park in the summer season and would be expressed in a high discomfort perception of its users. Thermo-physiological stress conditions in a typical summer month were compared with the subjective comfort perceptions of pedestrians surveyed in the park. It was found that even during mid-day hours, the level of thermal stress tends to be relatively mild, owing largely to the strong sea breeze and despite the high intensity of solar radiation. Moreover, it appears that the largely favorable perception of comfort among individuals may also result from socio-cultural aspects related to their satisfaction with the parks aesthetic attractiveness and in fact its very existence. Adaptive planning is proposed for such vulnerable regions, which are expected to experience further aggravation in thermal comfort due to global as well as localized warming trends.

Mediterranean weather conditions and exacerbations of multiple sclerosis.

Background: Previous studies provide increasing support for the impact of environmental factors on disease incidence and activity in multiple sclerosis (MS). Objectives: The purpose of this research was to assess the relationship between the incidence of MS relapses and weather conditions in Israel. Methods: Clinical data, including occurrence of relapses in 235 patients, during 3 consecutive years (2001–2003) were assessed against the general daily meteorological variables. Initially, the relationship between the relapses and their mode of distribution was evaluated. Second, the relationship between the number of relapses on a specific date and the meteorological variables was assessed. Third, the tendency to seasonality in the occurrence of relapses was examined. Results: No significant correlation was found between the number of relapses and a specific season, month or day. Moreover, no clear relationship was found between certain meteorological variables or a combination of variables and the frequency of the relapses. Conclusion: The meteorological parameters studied were not found to have a significant impact on the occurrence of relapses in this group of patients. These findings raise questions regarding the clinical significance of the impact of weather conditions, at least in the context of the Mediterranean climate, on the disease course of patients with MS.