Airports short-term forecasting of fog has a security and economic impact. Numerical simulations have been performed with the mesoscale model AROME (Application of Research to Operations at Mesoscale) (Seity et al. 2011). Three vertical resolutions (60, 90 and 156 levels) are used to show the impact of radiation fog on numerical forecasting. Observations at Roissy Charles De Gaulle airport are compared to simulations. Significant differences in the onset, evolution and dissipation of fog were found. The high resolution simulation is in better agreement with observations than a coarser one. The surface boundary layer and incoming long-wave radiations are better represented. A more realistic behaviour of liquid water content evolution allows a better anticipation of low visibility procedures (ceiling < 60m and/or visibility < 600m). The case study of radiation fog shows that it is necessary to have a well defined vertical grid to better represent local phenomena.

A statistical study over 6 months (October 2011 – March 2012 ) using different configurations was carried out. Statistically, results were the same as in the case study of radiation fog.

Seity Y., P. Brousseau, S. Malardel, G. Hello, P. Bénard, F. Bouttier, C. Lac, V. Masson, 2011: The AROME-France convective scale operational model. Mon.Wea.Rev., 139, 976-991.

Urban wind environment and thermal climate of cities in cold area have different properties compared to them in other regions, due to the unique characteristics of climatic features, building configuration and underlying surface composition. In this paper, a numerical approach which combines the urban region thermal climate prediction model with the snow cover-soil union heat transfer calculation model was proposed to study the wind environment and thermal climate of a residential area in Yichun, China. The numerical methods of these two models are demonstrated first, and then the outdoor wind velocity and temperature are dynamically calculated. The results show that local wind and thermal environments are influenced by snow cover, building volume rate and building height.

The main purpose of this work is to investigate the atmospheric processes over the cities of Western Siberia using a high-resolution mesoscale meteorological model TSU-NM3 developed at the Tomsk State University.

TSU-NM3 mesoscale model is not hydrostatic, it involves three-dimensional transient equations of the atmospheric boundary layer hydro-thermodynamics with the parametrization of turbulence, moisture microphysics, short-wave and long-wave (solar) radiation, advective and latent heat flows in the atmosphere and at the borderline of its interaction with the underlying surface.

TSU-NM3 mesoscale meteorological model [1] has been modernized by including a modern explicit representation scheme of moisture microphysics and by integrating the model with the computations by SL-AV global weather forecast model of the Meteorological Office of the Russian Federation in order to improve the computational accuracy.

TSU-NM3 mesoscale model has been used for predicting a thunderstorm and rainfall intensity on 27th August 2012 in the vicinity of airport of the City of Tomsk where meteorological instruments are used for monitoring the state of the atmosphere. The computations have been compared with the observations and computations made by Weather Research & Forecast model. The computation results have agreed well with the observations data and computations by WRF model [2]. Apart from that, the results by TSU-NM3 and WRF models used to predict extreme weather conditions in the vicinity of the airport of the City of Tomsk (severe frost in December 2012 and thawing weather in January 2013) have demonstrated a good correlation with the computations results when compared with the measurements made using modern instruments, i.e., МТР-5 temperature profile meter and WXT520 meteorological observing station.

This work was performed by order of the Ministry for education and science of the Russian Federation No. 5.628.2014/K.

Starchenko A.V. A numerical investigation of local atmospheric processes // Computational Technologies, 2005. V.10. p. 81–89. (in Russian)

Starchenko A.V., Belikov D.A., Vrazhnov D.A., Esaulov A.O. Application of MM5 and WRF mesoscale models to studies of region atmospheric processes // J. of Atmospheric and Oceanic Optics. - 2005, V.18, N. 05-06. - P. 455-461.

For urban climate modelling, land cover data are an important input. The quality of land cover data has an impact on simulation results. As an alternative to land cover data, the use of land use data might be possible. They are provided by urban planning authorities and represent the current utilization of land in respective areas. Nevertheless, most of the cities in Southeast Asia experience rapid urbanization associated with urban sprawl. This often leads to changes in urban landscape where abandoned open spaces occur even in the city center. These unauthorized spaces may not be represented by land use data. Land cover data, in contrast, show the actual situation on the ground and might be more suitable for simulation of urban climate. However, cities located in tropical regions are generally affected by high cloud cover throughout the year. Preparation of land cover data in areas severely affected by clouds requires a sophisticated approach and comprehensive tools.

This study compares the application of land cover and land use data for the simulation of urban climate in one major citiy in Southeast Asia. Johor Bahru is the capital of the Malaysian state Johor, which lies in the southern-most tip of Peninsular Malaysia.

For the preparation of land cover data, two Landsat 8 satellite images were used. These images were classified using supervised classification method. The performed land cover classification represents the actual land cover in the research area with an overall accuracy of 83% and 87%, respectively. The land use data for Johor Bahru were obtained from the Iskandar Regional Development Authority. These data represent the current situation in Johor Bahru as per the year 2012. The data on land cover and land use were used as land surface boundary for the Weather Research and Forecasting (WRF) model. The modelling of urban climate was performed with a spatial resolution of 0.5 km.

The simulation in WRF was conducted for one week in June 2013 during the southwest monsoon season. The simulation results were examined at three different locations with distinct features. In case of using land cover data, the maximum air temperature difference between the Central Business District (CBD) and rural area was up to 2.8 °C, while the maximum air temperature difference was around 2 °C between the CBD and residential area. In case of land use data, the simulation results show a tentative increase of the maximum air temperature of 0.5 °C in average for all locations. The air temperature difference between CBD and residential area was lower than in the case of land cover data. In general, the temperature increase in the CBD is particularly significant during nighttime. During daytime, temperature in CBD can fall below the values for residential and rural areas. These simulation results indicate the occurrence of Urban Heat Island formation in Johor Bahru.

Comparison of land cover and land use data for urban climate modelling shows that the use of land use data leads to an overestimation of simulation results. In particular, residential areas with lower building density experience an increase in temperature as compared with land cover data. This difference may occur due to the nature of land use data representing the planned utilization of allocated area. Abandoned open spaces or smaller vegetated pockets are not included in land use data. Changes of the urban landscape due to rapid development of cities in Southeast Asia are better represented by land cover data. However, for the general assessment of urban climate, land use data might still provide valuable results for the understanding of climate conditions.

Development and validation of urban-scale numerical weather and climate models requires better understanding of three-dimensional structure of urban heat island, including its shape and vertical thickness. An attempt to investigate 3D structure of the urban heat island of Moscow city, which forms the biggest urban agglomeration in Europe, was made during September-October 2014. Three similar MTP-5 microwave temperature profilers, which are available to measure temperature at the heights from 0 to 1000 meters with 50-m resolution, were install at three points in the city and its suburbs. These measurements were joined in single database with weather observations at more than 15 meteorological stations, located in the city and neighborhood, including meteorological observatory of Lomonosov Moscow State University.

Observations with MTP-5 profilers were taken one month. During this period, different weather conditions were observed, including periods of calm and clear anticyclonic weather, when urban heat island intensity at ground level reached values up to 8 ⁰C, with mean value about 1.8 ⁰C. Temperature difference between urban territory and suburbs over the surface, according MTP-5 measurements, was also significant (up to 2 ⁰C at several moments) until the height of 1000 m.

Measurements of temperature profilers were used for data assimilation in numerical experiments with WRF (Weather Research & Forecasting) model, launched with resolution about 1 km for Moscow region. The effect of data assimilation on forecast quality for rural and urban territories was examined and evaluated. Observations of the MTP-5 temperature profilers and meteorological stations and modelling results were used for investigation of the 3-dimentional structure of urban heat island and It’s dependence on synoptic conditions and wind direction.

The study was supported by Russian Scientific Fund (RSF), project №14-27-00134