Wyniki wyszukiwania - BazTech

1

Mesoscale Convective Systems monitoring on the basis of MSG data - case studies

Szafranek K., Jakubiak B., Lech R., Tomczuk M.

Artificial Satellites : Journal of Planetary Geodesy

|

2015

|

Vol. 50, No. 2

91--103

EN

Analysis described in the paper were made in the frame of the PROZA (Operational decisionmaking based on atmospheric conditions, http://projekt-proza.pl/) project co-financed by the European Union through the European Regional Development Fund. One of its tasks was to develop an operational forecast system, which is going to support different economies branches like forestry or fruit farming by reducing the risk of economic decisions with taking into consideration weather conditions. The main purpose of the paper is to describe the method of the MCSs (Mesoscale Convective Systems) tracking on the basis of the MSG (Meteosat Second Generation) data. Until now several tests were performed. The Meteosat satellite images in selected spectral channels collected for Central Europe Region for May 2010 were used to detect and track cloud systems recognized as MCSs in Poland. The ISIS tracking method was applied here. First the cloud objects are defined using the temperature threshold and next the selected cells are tracked using principle of overlapping position on consecutive images. The main benefit of using a temperature threshold to define cells is its efficiency. During the tracking process the algorithm links the cells of the image at time t to the one of the following image at time t+dt that correspond to the same cloud system. Selected cases present phenomena, which appeared at the territory of Poland. They were compared to the weather radar data and UKMO UM (United Kingdom MetOffice Unified Model) forecasts. The paper presents analysis of exemplary MCSs in the context of near realtime prediction system development and proves that developed tool can be helpful in MCSs monitoring.

2

Experiments with three-dimensional radar reflectivity data assimilation into the COAMPS model

Jakubiak B., Szturc J., Ośródka K., Jurczyk A.

Meteorology Hydrology and Water Management. Research and Operational Applications

|

2014

|

Vol. 2, Iss. 1

43--54

EN

High temporal and spatial resolution of radar measurements enables to continuously observe dynamically evolving meteorological phenomena. Three-dimensional (3D) weather radar reflectivity data assimilated into the numerical weather prediction model has the potential to improve initial description of the atmospheric model state. The paper is concentrated on the development of radar reflectivity assimilation technique into COAMPS mesoscale model using an Ensemble Kalman Filter (EnKF) type assimilation schemes available in Data Assimilation Research Testbed (DART) programming environment. Before weather radar data enter into the assimilation system, the measurement errors are eliminated through quality control procedures. At first artifacts associated with non-meteorological errors are removed using the algorithms based on analysis of reflectivity field pattern. Then procedures for correction of the reflectivity data are employed, especially due to radar beam blockage and attenuation in rain. Each of the correction algorithms is connected with generation of the data quality characteristic expressed quantitatively by so called quality index (QI). In order to avoid transformation of data uncertainty into assimilation scheme only the radar gates successfully verified by means of the quality algorithms were employed in the assimilation. The proposed methodology has been applied to simulate selected intense precipitation events in Poland in May and August 2010.

3

Rainfall estimates from radar vs. raingauge measurements. Warsaw case study

Jakubiak B., Licznar P., Malinowski S. P.

Environment Protection Engineering

|

2014

|

Vol. 40, nr 2

159--170

EN

Contemporary models of urban hydrology and especially hydrodynamic models of stormwater systems demand on supply with high resolution spatial and temporal precipitation information. A plausible solution of precipitation information acquiring over urban catchments is seen in coupling of radar signals and raingauge networks measurements. Suitability of this approach is tested in the case of standard C-band weather radar and the dense network of fast-response raingauges. Rainfall rate estimated based on dependence on the reflectivity factor (Z-R relationship) in single pixels of the radar image are compared to rainfall rates measured by 25 raingauges located in Warsaw, Poland. In the analyzed period, 23 precipitation days with rain from convective clouds and cloud systems are detected. The main conclusion is that despite the fact that adopted Z-R relationship holds well in statistical sense (i.e. the whole period long empirical probability distribution functions (PDFs) of estimated and measured rainfall rates are in good agreement), instantaneous measurements and estimates as well as short-term (one day) PDFs differ remarkably. These differences are not systematic, they vary from the raingauge to raingauge and from day to day. Moreover, the most remarkable differences are associated with the highest rainrates which should be carefully considered prior radar data use as input for urban hydrology modelling.

4

Impact of the surface temperature and vertical shear of zonal wind on the dynamics of a simple two-layer model of the atmosphere

Brojewski R., Jakubiak B., Jasiński J.

Acta Geophysica

|

2007

|

Vol. 55, no. 2

231-252

EN

The paper presents and analyzes, from the point of view of smooth dynamic systems theory, a two-layer baroclinic model of the troposphere in geostrophic approximation. The model describes airflow in β-channel within the tropospheric part of the main Hadley circulation cell. It enables to obtain, after application of the Galerkin method, a fairly simple low-parametric dynamic system describing the phenomena of nonlinear interactions, bifurcations and blocking in the atmosphere. This enables to take into consideration such basic factors influencing the atmospheric dynamics like the heat exchange within the surface, orography, vertical variability of zonal wind and hydrostatic stability. Impact of zonal thermal variability of the surface and vertical shear of zonal wind in the troposphere on the orographic bifurcation was investigated and the oscillation character in the dynamic system after Hopf bifurcation of the second kind was analyzed. Additionally, the model dynamics was investigated in conditions in-cluding momentum forcing in the upper and lower parts of the troposphere and excluding orographic interaction, as well as in the conditions of thermal interaction between the troposphere and the surface for the vertical shear of zonal wind in both tropospheric layers. Impact of the mean zonal wind in the troposphere on the prop-erties of model dynamics was assessed. It was proved that zonally varied surface temperature and layered mean zonal wind in the atmosphere are the parameters that have basic influence on the model dynamics. They cause numerous bifurcations and strongly influence the periods of oscillations of the model variables. They are often Hopf bifurcations of the second kind during which tropospheric states fairly distant from the ones before the bifurcations are generated. This significantly influences the model predictability.

5

Agrometeorologiczny system wspomagania decyzji w organizacji prac gospodarstw rolnych w Wielkopolsce - etap pierwszy tworzenia serwisu

Juszczak R., Leśny J., Olejnik J., Jakubiak B., Friesland H.

Woda-Środowisko-Obszary Wiejskie

|

2005

|

T. 5, z. 2

157-173

PL

W pracy przedstawiono koncepcję pierwszego w Wielkopolsce i drugiego w Polsce internetowego serwisu informacji agrometeorologicznej, mającego stanowić system rolniczego wspomagania decyzji w organizacji prac gospodarstw rolnych. Serwis ten będzie obejmował swym zasięgiem rolników w Wielkopolsce i południowej części województwa kujawsko-pomorskiego. Zasadniczym elementem udostępnianej rolnikom informacji agrometeorologicznej będzie prognoza pogody generowana przez model UMPL, pracujący od 1997 r. w Interdyscyplinarnym Centrum Modelowania Matematycznego Uniwersytetu Warszawskiego. Stworzona sieć automatycznych stacji meteorologicznych ma dostarczać danych, które po zasymilowaniu do modelu UMPL poprawią jakość prognozy meteorologicznej. Na jej podstawie będzie tworzona prognoza agrometeorologiczna, składająca się z informacji o najbardziej odpowiednich terminach wykonywania najważniejszych zabiegów agrotechnicznych (siewu i zbioru roślin uprawnych, koszenia i zbioru traw, wykonywania zabiegów chemicznej ochrony roślin). O potrzebie tworzenia takiego serwisu świadczą wyniki przeprowadzonych badań ankietowych, z których jednoznacznie wynika, że rolnicy w Wielkopolsce są bardzo zainteresowani tego typu informacjami.

EN

The concept of the Internet service of agrometeorological information which will be the first one in the Wielkopolska Region and the second in Poland is presented in this paper. This service will play a major function in agricultural decision support system useful for organization of daily work in farms involved in the project. The Internet agrometeorological service will be useful and available for farmers in the Wielkopolska Region and the southern part of the Kujawsko-Pomorskie region. A fundamental element of agrometeorological information addressed to farmers will be the weather forecast produced by the UMPL model, which has been working in the ICM of Warsaw University since 1997. Created network of automatic weather stations will deliver data, which after assimilation to the UMPL model should improve the quality of weather forecast. On the basis of this forecast the agrometeorological forecast will then be created. This agrometeorological forecast will mainly include information on the optimal dates of most important agrotechnical activities (sowing, harvesting, mowing of grass, spraying etc.). Results of questionnaire carried out in the Wielkopolska Region in 2002 indicate the urgent need of this kind of agricultural service development.

6

Dynamics of a 2L-baroclinic model of the troposphere. Part 2: impact of the zonal drift on bifurcations in the model

Brojewski R., Jakubiak B., Jasiński J.

Journal of Technical Physics

|

2005

|

Vol. 46, no 4

203-218

EN

The paper presents results of numerical analyses related with assessment of the impact of mean zonal drift in the troposphere on the properties of the dynamics of a simple two-layer model of the baroclinic troposphere. It was proved that the model dynamics is mainly influenced by zonally differentiated surface temperature. It causes numerous bifurcations. They are often Hopf bifurcations of the second kind during which tropospheric states quite distant from the states before the bifurcations are generated. It significantly influences the model predictability. The paper contributes to the assessment of applicability of hydrodynamic models to weather forecasting for periods longer than two weeks.

7

Dynamics of a 2L-baroclinic model of the troposphere. Part 1: Thermal bifurcation and blocking

Brojewski R., Jakubiak B., Jasiński J.

Journal of Technical Physics

|

2005

|

Vol. 46, no 3

131-147

EN

The paper analyzes, from the point of view of the theory of smooth dynamic systems, a simple two-layer model of baroclinic atmosphere applied within the main Hadley cell of circulation. The dynamics of the model was investigated in conditions excluding orographic influence but including momentum forcing in the upper and lower layers of the troposphere and thermal interaction between the troposphere and the surface for various vertical differentiations of the zonal drift in two tropospheric layers. The obtained results contribute to a profound view onto the applicability of classical weather forecasting models based on the hydrodynamic attitude.

8

Impact of the surface temperature and the zonal drift on the orographic bifurcation and blocking in 2l-baroclinic model of the troposphere

Brojewski R., Jakubiak B., Jasiński J.

Journal of Technical Physics

|

2004

|

Vol. 45, no 3

217-235

EN

The paper presents a 2-layer baroclinic model of the troposphere in geostrophic approximation that enables to obtain, after application of the Galerkin method, a fairly simple low-parametric dynamic system describing the phenomena of nonlinear interactions, bifurcations, blocking and auto-regulation in the atmosphere. It enables to take into consideration such basic factors molding the atmospheric dynamics like heat exchange with the surface, orography, vertical diversity of the zonal drift and hydrostatic stability. Conditions oforographic bifurcation of the model were investigated and confronted with the results obtained from a barotropic model. Impact of the zonal thermal diversity of the surface and the vertical diversity of the zonal drift of the troposphere on the orographic bifurcation was assessed. Oscillation character analysis was made in the dynamic system after Hopf bifurcation of the second kind.

9

Assessment of numerical wind forecasts for the Gdańsk bay area during the POLRODEX'97 experiment

Kałas M., Jakubiak B.

Biuletyn Instytutu Morskiego w Gdańsku

|

1999

|

Vol. 26, No. 1

13--25

EN

The paper presents results of forecasts of wind field parameters over the Baltic Sea for the Gdańsk Bay area obtained using two atmosphere models: UMPL (ICM Warsaw University) and HIRLAM (SMHI Sweden). The obtained results are compared with field observations made on the open sea and at coastal stations during the POLRODEX'97 experiment. The agreement is quite good, although the influence of local weather conditions cannot be neglected.