Wyniki wyszukiwania - BazTech

1

Uwarunkowania cyrkulacyjne zachmurzenia ogólnego w strefie polarnej Europy

Adamczyk R., Ustrnul Z

Problemy Klimatologii Polarnej

|

2008

|

nr 18

79-88

PL

Analizowano wielkość zachmurzenia ogólnego w zależności od kierunku adwekcji mas powietrza. Materiał badawczy stanowiły dane gridowe pochodzące z bazy danych ERA 40 (1961-2000) oraz dane stacyjne z bazy danych ORNL/CDIAC – 123 NDP-026C (1972-1996). Cyrkulację atmosferyczną ujęto jako obraz pola wiatru geostroficznego. Warunki makrocyrkulacyjne powodują duże zróżnicowanie regionalne wzajem-nych zależności pomiędzy cyrkulacją a zachmurzeniem na badanym terenie. Różnice wielkości zachmurzenia podczas adwekcji mas powietrza z poszczególnych kierunków są bardziej wyraźne w analizach wykorzystują-cych dane stacyjne. Występujące różnice między wynikami analiz przeprowadzonych z wykorzystaniem danych gridowych i stacyjnych wynikają głównie z trudności w dopasowaniu położenia stacji do punktów węzłowych siatki geograficznej oraz z samego charakteru danych.

EN

The main aim of the study was the quantitative estimation of the influence of the air advection on the total cloudiness in the European polar zone. The area of interest was defined as the region located over the northern polar circle. That territory covers the large part of the Arctic Ocean with the arctic archipelagos such as: Spitsbergen, Franz Josef Land, Novaya Zemlya, and the separate islands. The northern part of the Scandinavian Peninsula with the Kola Peninsula were also taken into considerations. The source data contain daily total cloudiness data originated from reanalyses ERA-40 (developed by ECMWF) for the period 1961-2000. Simultaneously, daily resolution station data from 5 stations originated from CDIAC database for the period 1972-1996 have been taken into account. Atmospheric circulation was performed as the geostrophic wind field. Geostrophic wind vectors were calculated using splines and on their basis the 9 main circulation types were distinguished (modified Ustrnul’s circulation classification). The crucial method was the calculation of anomalies of the total cloud cover in particular air flow types in two thermal and circulation different months: January and July. The analysis of cloudiness showed large regional diversity of this element in the polar zone of Europe. The relations of the total cloud cover with atmospheric circulation in maritime area were weaker than in the continental parts of research domain. On the basis of many cases was founded that cloudiness was also under influence of orography, type of the active surface, sea and atmosphere interactions. Large scale circulation with the mentioned factors causes significant regional differen-tiation of mutual connections between cloudiness and geostrophic wind vector.

2

Satelitarna charakterystyka zachmurzenia ogólnego nad Svalbardem w roku 2007 w powiązaniu z cyrkulacją atmosfery

Kotarba A., Widawski A.

Problemy Klimatologii Polarnej

|

2008

|

nr 18

127-140

PL

W artykule przedstawiono rozkład czasowy i przestrzenny zachmurzenia ogólnego nad Sval-bardem w 2007 r. Wszystkie prezentowane wielkości zachmurzenia wyliczono z maski chmur, będącej jednym z produktów powstałych w wyniku przetworzenia danych satelitarnych radiometru MODIS, umieszczonego na satelitach Terra i Aqua. Analizie poddano średnie miesięczne, średnią roczną oraz średnie zachmurzenie w po-szczególnych 11 typach uproszczonej klasyfikacji Niedźwiedzia, tak dla całej powierzchni archipelagu, jak i jego poszczególnych części.

EN

One of the fundamental problems in cloud climatology research is a lack of high spatial and temporal resolution data. Conventional, surface-based visual observations are limited to a small number of locations and represent atmospheric conditions only within a small vicinity of the stations. This is particularly true in the Arctic, which is inadequately sampled due to extreme weather condi-tions and maritime character of this area. As an alternative, satellite data can be utilized as a base for cloud climatology studies. In this paper Moderate Resolution Imaging Spectroradiometer (MODIS) observations are used as a source of cloud data for investigating the relation between total cloud cover and atmospheric circulation patterns over Svalbard. MODIS data were obtained as a Cloud Mask product – a 1 km resolution raster with four classes reflecting cloud detection confidence: 'confident clear', 'probably clear', 'uncertain clear' and 'certain cloudy'. Each class was arbitrary turned into fractional cloud cover as 0%, 33%, 66% and 100% respectively. Total number of 5607 MODIS passes over Svalbard was analyzed (about 16 a day). Area of study was divided into three regions – Spitsbergen (1) with subregions: 1a (north-western part), 1b (north-eastern part), 1c (southern part); Nordaustlandet (2); Barents Island and Edge Island (3). Mean monthly and annual cloud amount was calculated for each region as a ratio of cloudy pixels (weighted by 0%, 33%, 66% and 100%) to all pixels within given region/subregion. MODIS-derived information was then set against Niedźwiedź (2007) circulation type classification. Classification is an application of Lamb (1972) subjective classification, reduced in this study from 21 to 11 types: 5 cyclonic, 5 anticyclonic and 1 undetermined. As the results show, mean total cloud cover over Svalbard in 2007 amounted to 74%, varying from 61% in February up to 85% in August. The greatest mean monthly cloud cover (88%) was observed over Nordaustlandet in August, while the lowest (57%) over southern part of Spitsbergen in February. The cloudiest parts of Svalbard in 2007 were Nordaustlandet and Edge Island with 76% and 77% of annual mean cloud cover respectively – slightly more than Spitsbergen (73%). Spatial distribution of annual mean cloud cover Svalbard was controlled by topography and atmospheric circulation conditions. Atmospheric circulation over Svalbard in 2007 was dominated by advection from N-E-S directions and non-advective situations (center of cyclone or cyclonic trough). Average cloud cover was nearly constant throughout all circulation types, ranging from 74% (cyclonic advection from S+SE) to 77% (cyclone's center or cyclonic trough). Most diverse spatial distribution of cloud cover was observed during the days of central anticyclonic situations and anticyclonic wedge, while least diverse when cyclone's center, cyclonic trough or anticyclonic advection from S+SW occurred. MODIS-derived cloud cover variability can be well explained by circulation influence, e.g. foehn effect associated with anticyclonic E+SE advection, cloud amount increase as a result of S+SW or W+NW cyclonic advection from Norwegian Sea. Although annual course of cloud cover, as determined with satellite information, seems reliable, future studies should emphasise a comparison of MODIS data with surface based observations. Temporal coverage should be also expanded to years 2003-2008 in order to obtain statistically significant results.

3

Sumy dzienne promieniowania słonecznego w okresie letnim w Felinie koło Lublina i ich związek z usłonecznieniem i zachmurzeniem

Kossowski J., Łykowski B.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

|

2007

|

Vol. 16, No. 1

74--84

EN

The paper presents the relationships between daily sums of global solar radiation and real sunshine duration and separately, mean for a day amount of total cloudiness (computed from three standard observation terms) within 11 May - 31 July period in Felin. This period is approximated to the insolation summer one and is characterised by a long day (at least 15.5) and slight differentiation in time. The relationships were obtained on the basis of mean decade data and a stretch of single days during five seasons (but not successive). They were described with two types of equation regressions: linear and curvilinear (a 2-degree polynomial). Additionally, the same relationships were determined regarding the days without and with precipitation during the examind summer periods. The analysis performed in relation to effectiveness of each of these equations application to estimate daily sums of global solar radiation (the relative and standard errors) showed that better results are obtained from the equations concerning relations of the solar radiation with sunshine duration than cloudiness. It also reveated that to describe both types of the relationships, a polynomial is more effi cient than linear regression (particularly in the case of daily data examination). Moreover, it was stated that determination of these relationships for some specific days (eg. days without precipitation) is appropriate as it allws to estimate the daily sum of solar radiation with smaller errors.