Impact of the Darjeeling–Bhutan Himalayan front on rainfall hazard pattern

Multiscale interaction between monsoonal circulation and the local topography causes the southern front of the Darjeeling–Bhutan Himalaya to receive one of the highest annual rainfalls (3000–6000 mm) and most frequent heavy rains (up to 800 mm day^?1) along the whole southern Himalayan margin. An examination of the patterns of annual rainfall, rainfall concentration, overland flow generation and slope instability indices in the Darjeeling–Bhutan Himalaya for 1986–2015 indicates that the mountain front disturbs rainfall gradient between the Bay of Bengal and the Tibetan Plateau. The results show that the precipitation concentration indices are lowest at the Himalayan front where the annual rainfall and the number of rainy days are highest. The Himalayan front has the highest predisposition to produce overland flow compared to adjacent foreland and the mountain interior. The average probability of the rainfall initialising the shallow landslides increases from 0.6% for a 1-day rainfall threshold of 144 mm to 6.1% for a 4-day rainfall threshold of 193 mm in the study area. The highest probability (up to 10%) of 2-day and longer low-intensity storms at the mountain front indicate that its area is threatened with particularly larger and deeper landslides. The multivariate regression analysis reveals statistically significant linear relationships of rainfall hazard indices with elevation and the distance to the mountain front in the mountain foreland and Himalaya, respectively. Regionally, the Darjeeling Himalaya reveals lower values of rainfall hazard indices, in comparison to the Bhutan Himalaya.     

Analysis of long-range network RTK during a severe ionospheric storm

The network-based GPS technique provides a broad spectrum of corrections to support RTK (real-time kinematic) surveying and geodetic applications. The most important among them are the ionospheric corrections generated in the reference network. The accuracy of these corrections depends upon the ionospheric conditions and may not always be sufficient to support ambiguity resolution (AR), and hence accurate GPS positioning. This paper presents the analyses of the network-derived ionospheric correction accuracy under extremely varying – quiet and stormy – geomagnetic and ionospheric conditions. In addition, the influence of the correction accuracy on the instantaneous (single-epoch) and on-the-fly (OTF) AR in long-range RTK GPS positioning is investigated, and the results, based on post-processed GPS data, are provided. The network used here to generate the ionospheric corrections consists of three permanent stations selected from the Ohio Continuously Operating Reference Stations (CORS) network. The average separation between the reference stations was ∼200 km and the test baseline was 121 km long. The results show that, during the severe ionospheric storm, the correction accuracy deteriorates to the point when the instantaneous AR is no longer possible, and the OTF AR requires much more time to fix the integers. The analyses presented here also outline the importance of the correct selection of the stochastic constraints in the rover solution applied to the network-derived ionospheric corrections.     

Moment magnitude determination of local seismic events recorded at selected Polish seismic stations

The paper presents the method of local magnitude determination used at Polish seismic stations to report events originating in one of the four regions of induced seismicity in Poland or its immediate vicinity. The method is based on recalculation of the seismic moment into magnitude, whereas the seismic moment is obtained from spectral analysis. The method has been introduced at Polish seismic stations in the late 1990s but as of yet had not been described in full because magnitude discrepancies have been found between the results of the individual stations. The authors have performed statistics of these differences, provide their explanation and calculate station corrections for each station and each event source region. The limitations of the method are also discussed. The method is found to be a good and reliable method of local magnitude determination provided the limitations are observed and station correction applied.     

Heavy metals in sediments as evidence for recent pollution and quasi-estuarine processes: an example from Lake Druzno,Poland

This article presents the results of a geochemical investigation of sediments from Lake Druzno (northern Poland), a reservoir fed by freshwater from the catchment, with periodic input of brackish water from Vistula Lagoon. This study analyzed the spatial variation in heavy metal content in surface sediments as well as the temporal changes in metal content in two sediment cores dated using the ²¹⁰Pb method. In the surface sediments, the highest metal concentrations were recorded in the northern part of the lake, with lower concentrations in the central and southern parts. Absolute values of metal concentrations in the cores were low, but normalization with respect to Al showed an increase during the second half of the 20th century. Mean enrichment factors (EF) in sediments from the second half of the 20th century ranged from insignificant (1–1.2) for Fe to (1.55–3.3) for Cu, Cd, Pb and Zn. The sediments deposited before 1950 had lower EF values (>1.5) and had low variability. Results from both the surface sediments and the cores indicate that the main source of lake pollution is brackish water intrusion from the Vistula Lagoon via the contaminated River Elbląg.     

Podhale,Poland, earthquake of November 30, 2004

Earthquake of November 30, 2004, in Podhale region, southern Poland, was of unexpectedly big size in this area of weak seismicity. As Poland is considered a country of low seismicity, the earthquake has caused concern about seismic hazard in Poland, especially since it took place shortly after the even more unexpected Kaliningrad Region, Russia, earthquakes of September 21, 2004, that inflicted minor damage in northern Poland. The paper presents the findings on the Podhale earthquake which reached macroseismic intensity up to 7 and magnitude 4.7 (m _b ; ISC). The event was felt up to a distance of about 100 km and inflicted slight damage to buildings in its narrow epicentral area, thus evidencing its relatively shallow depth. The quake has been located near the village of Skrzypne, about 15 km west-southwest of the district capital Nowy Targ. The source mechanism has been found to be of dip slip normal fault type, although a problem remains of association of this mechanism with known tectonic dislocations in the region. The earthquake has been followed by a long series of aftershocks. Their distribution in time is also studied and the biggest aftershocks have been located.     

Measurement of aerosol optical thickness over the Atlantic Ocean and in West Antarctica, 2006–2007

In this paper, optical measurements of aerosol properties made during a ship cruise from Poland to Antarctic Station in September and October 2006, and during the cruise back to Gdynia in April and May 2007 are described. A large gradient of pollution between the clear South Atlantic and the dusty North Atlantic was observed. The maximum of aerosol optical thickness at a wavelength of 500 nm reached 0.4 at 20°N in September 2006 and 0.3 at 40°N in May 2007, respectively. Strong Saharan dust transport is suggested as an explanation for the small values of Ångström exponent observed (values of 0.2 and 0.4 on these respective dates). On the Southern Hemisphere the aerosol optical thickness at 500 nm ranged from 0.05 to 0.2. Significant increases of the aerosol optical thickness were associated with strong wind and sea salt production. Good agreement was found when the in situ measurements of aerosol optical thickness were compared to satellite retrievals and modelling results.     

Meteorological study of the first observation of red sprites from Poland

The first red sprite events scientifically observed from Poland on 20/21 July 2007, during the two-week SPARTAN Sprite-Watch 2007 campaign, are analysed in the context of the meteorological conditions over Poland and the Czech Republic at that time. The phenomena were detected and recorded from the IMWM High-Mountain Meteorological Observatory at Mount Śnieżka using a low-light television CCD camera. Meteorological conditions over the south-west Poland were monitored on the basis of information from the Polish and Czech meteorological radar and lightning detection systems and also from satellite infra-red difference images, indicating the development of thunderstorm clouds over central Europe. Four sprite events detected in the night-time of 20/21 July indicate that in this region sprites are produced by massive storm cells built on warm fronts which are supplied by warm and humid tropical air masses during local summer thunderstorm season.     

Assessment of climate change and associated impact on selected sectors in Poland

The present paper offers a brief assessment of climate change and associated impact in Poland, based on selected results of the Polish–Norwegian CHASE-PL project. Impacts are examined in selected sectors, such as water resources, natural hazard risk reduction, environment, agriculture and health. Results of change detection in long time series of observed climate and climate impact variables in Poland are presented. Also, projections of climate variability and change are provided for time horizons of 2021–2050 and 2071–2100 for two emission scenarios, RCP4.5 and RCP8.5 in comparison with control period, 1971–2000. Based on climate projections, examination of future impacts on sectors is also carried out. Selected uncertainty issues relevant to observations, understanding and projections are tackled as well.     

2002 AA29: Earth's recurrent quasi-satellite?

We study the dynamical evolution of Asteroid 2002 AA₂₉. This object moves in the co-orbital region of the Earth and is the first known asteroid which experiences recurrent horseshoe-quasi-satellite transitions. The transitions between the HS and QS states are unique among other known Earth co-orbital asteroids and in the QS state 2002 AA₂₉ remains very close to Earth (within 0.2 AU for several decades [Connors, M., Chodas, P., Mikkola, S., Wiegert, P., Veillet, C., Innanen, K., 2002. Meteorit. Planet. Sci. 37, 1435-1441]). Based on results obtained analytically by Brasser et al. [Brasser, R., Heggie, D.C., Mikkola, S., 2004b. Celest. Mech. Dynam. Astron. 88, 123-152] we developed a simple analytical method to describe and analyze the motion of 2002 AA₂₉. We distinguish a few moments in time crucial for understanding its dynamics. Near 2400 and 2500 this object will be close to going through the maxima of the averaged disturbing function and it will either change its co-orbital regime by transition from the HS into QS state, or leave the librating mode. These approaches generate instability in the motion of 2002 AA₂₉. By means of 66 observations, covering a two-year interval, we extend the analysis of the long term evolution of this object presented by Connors et al. [Connors, M., Chodas, P., Mikkola, S., Wiegert, P., Veillet, C., Innanen, K., 2002. Meteorit. Planet. Sci. 37, 1435-1441] and Brasser et al. [Brasser, R., Innanen, K.A., Connors, M., Veillet, C., Wiegert, P., Mikkola, S., Chodas, P.W., 2004a. Icarus 171, 102-109]. Our analysis is based on a sample of 100 cloned orbits. We show that the motion of 2002 AA₂₉ is predictable in the time interval [−2600,7100] and outside of this interval the past and future orbital history can be studied using statistical methods.