Extended Abstract:

Introduction

A simple study of the environment reveals that cities have expanded greatly in both the horizontal and vertical directions over the past two or three decades. This problematic phenomenon has caused the areas that in the not so distant past were full of various plants to be replaced with dark concrete and asphalt. This has a tremendous impact on the weather in different parts of the city, from a micro-meteorological point of view (small-scale meteorology). One of the obvious consequences is an increase in temperature in places that have more and more dense buildings in particular, and vegetation has a low density. Urban heat island development occurs when a large portion of the earth's natural vegetation in an area is replaced by man-made surfaces, resulting in low moisture due to lack of vegetation and impermeable surfaces absorbing large amounts of solar radiation during the day and then during the night Is reflected. In one city, the temperature is often 3 to 4 degrees Celsius higher than in other non-urban areas.The difference between the temperature of the heat waves and the environment around the intensity of the heat waves is called so that the higher the temperature of the heat waves than the environment, the higher the intensity of the heat waves, the intensity of urban heat waves can vary between 0 to 7 degrees Celsius depending on the season, sunlight and city characteristics. On a hot summer day, the sun warms homeless, dry surfaces such as rooftops and hard street surfaces, sometimes up to 20 to 50 degrees Celsius, while shady or humid surfaces, often on the outskirts of the city, have temperatures around the temperature. They have air. Urban heat islands exist during the day and night, but are more intense during the day when the sun shines.

Materials and Methods

Tehran province is located in the center of Tehran, with an area of about 12981 square kilometers, between 34 to 36.5 degrees north latitude and 50 to 53 degrees east longitude. This province is limited to Mazandaran province from the north, Qom province from the south, Markazi province from the southwest, Alborz province from the west and Semnan province from the east. The capital of this province is Tehran. Tehran is also the capital of Iran. District 6 of Tehran is one of the relatively old districts of Tehran, which is geographically located in the central part of Tehran. In order to verify the information obtained from this study, the obtained data were compared with the data of the Geophysic Synoptic Station of the University of Tehran. This station is very close to the study area and this is the reason for its selection. Land surface temperature can be described as; the sensation of heat when the ground is touched by hand or skin. The Land surface temperature is finally calculated by the following equation.

T_s=TB/(1+(λ × TB/ρ)Lnε)

The following equation is used to convert surface temperature to air temperature.

Ta=0/14+6/44×LST

Results and discussion

Table 4, Validation of information obtained

seasons Geophysical station air temperature (℃) Calculated air temperature (℃) Temperature difference (℃)

Autumn 8/6 11/2 2/6

Winter 5/2 4/18 1/02

Spring 18/3 17/2 1/1

Summer 30/11 28/74 1/37









In order to validation the results obtained from the study and the data of the Geophysical Station of the University of Tehran were compare and the following table is presented.





















Figure 3 Temperature map of district 6 of Tehran

Figure (3) shows the temperature map in summer, this map is classified into 5 temperature levels and temperatures above 30 ° C have been identified as thermal islands. Green areas indicate temperatures below 27.5 ° C, the average temperature in summer is 28.36 and the average temperature of the heat islands in summer is 30.24 ° C and the average intensity of the heat islands is 1.88 degrees Celsius.

























Figure 4 Map of vegetation and Heat islands of District 6 of Tehran City

In places where there is good and dense vegetation, the temperature is lower and the reason for the low temperatures of the temperature map is the presence of vegetation.

Conclusion

Based on the results of this study, it can be summarized that one of the main reasons for the temperature balance in an environment is the presence of vegetation, and in the absence of it, the ambient temperature increases and using vegetation in areas where the intensity Heat islands are high and rising, can help lower the temperature. The reason for this can be summarized as follows: by changing the materials of urban surfaces and increasing the permeability of water and moisture, which is all achieved by replacing these surfaces with plants, and as a result, plants heat later than impermeable surfaces such as asphalt and concrete.