Search results for "Summer"
showing 10 items of 58 documents
Evidence for marine biogenic influence on summertime Arctic aerosol
2017
International audience; We present vertically-resolved observations of aerosol composition during pristine summertime Arctic background conditions. The methansulfonic acid (MSA)-to-sulfate ratio peaked near the surface (mean 0.10), indicating a contribution from ocean-derived biogenic sulfur. Similarly, the organic aerosol (OA)-to-sulfate ratio increased towards the surface (mean 2.0). Both MSA-to-sulfate and OA-to-sulfate ratios were significantly correlated with FLEXPART-WRF-predicted airmass residence time over open water, indicating marine influenced OA. External mixing of sea salt aerosol from a larger number fraction of organic, sulfate and amine-containing particles, together with lo…
Interannual memory effects for spring NDVI in semi-arid South Africa
2008
[1] Almost 20 years of Normalized Difference Vegetative Index (NDVI) and precipitation (PPT) data are analysed to better understand the interannual memory effects on vegetation dynamics observed at regional scales in Southern Africa (SA). The study focuses on a semi-arid region (25°S–31°S; 21°E–26°E) during the austral early summer (September–December). The memory effects are examined using simple statistical approaches (linear correlations and regressions) which require the definition of an early summer vegetation predictand (December NDVI minus September NDVI) and a consistent set of potential predictors (rainfall amount, number of rainy days, rainfall intensity, NDVI and Rain-Use-Efficie…
Summer time predation on the obligatory off-host stage of an invasive ectoparasite
2016
SUMMARYPredation can regulate populations and strongly affect invasion success of novel prey. The deer ked (Lipoptena cervi; Linnaeus 1758) is an invasive ectoparasite of cervids that spends a long period of its life cycle outside the host. Prior to this study, virtually nothing was known about natural summer time predation on the deer ked. We aimed to evaluate the magnitude of summer time predation onL. cervipupae in different habitats and to identify potential predators. We conducted a set of field experiments, where we exposedL. cervipupae to various ground-dwelling vertebrate and invertebrate predators. The loss of pupae was monitored for different predator guilds. Three habitats of the…
Developing common protocols to measure tundra herbivory across spatial scales
2021
Understanding and predicting large-scale ecological responses to global environmental change requires comparative studies across geographic scales with coordinated efforts and standardized methodologies. We designed, applied and assessed standardized protocols to measure tundra herbivory at three spatial scales: plot, site (habitat), and study area (landscape). The plot and site-level protocols were tested in the field during summers 2014-2015 at eleven sites, nine of them comprising warming experimental plots included in the International Tundra Experiment (ITEX). The study area protocols were assessed during 2014-2018 at 24 study areas across the Arctic. Our protocols provide comparable a…
Melosira distans var. tenella and Eunotia zasuminensis, two poorly known planktonic diatoms in Finnish lakes
1986
The occurrence and ecology of two poorly known planktonic diatoms, Melosira distans var. tenella (Nyg.) M.-B. Florin and Eunotia zasuminensis (Cabejsz.) Korner in central Finland is discussed. Both species have their maximum in late summer when water temperature is > 15°C and they prefer slightly acid water (pH < 7), low conductivity (less than 4 mS/m) and a moderate degree of dystrophy with C.O.D. 10–20 mg O2/l and water colour 60–120 mg Pt/1. Melosira distans var. tenella was found in ca. 80% of the central Finnish lakes studied, but it is not reported in previously published papers. Eunotia zasuminensis is rarer, but is, however, recorded in at least 22 lakes in central Finland.
Impact of Different Building Materials on Summer Comfort in Low-Energy Buildings
2015
Abstract The aim of the current paper is to analyse thermal comfort and overheating risks in the low-energy buildings in a summer season under Latvian climate conditions both experimentally and numerically. An interior temperature and relative humidity are analysed under free-floating conditions. Two cases are analysed: in one case, the solar influence through the window is taken into account; in the other this influence is omitted. Three different building solutions are observed: two building structures which mainly consist of the mineral wool and wooden materials and one structure from aerated clay bricks and mineral wool. The experiments have been implemented in test stands in Riga, Latv…
Aparatūra “Lotoss” poliuretāna plastmasas detaļu atliešanai kosmosā
2020
1980. gadā kosmosa stacijā “Salūts” pirmoreiz kosmonautikas vēsturē tika realizēts putupoliuretāna ieguves eksperiments mikrogravitācijas apstākļos, kura rezultāta tika iegūtas jaunas atziņas par ķīmiski tehnoloģisko procesu norisi kosmosā. Kosmosā tapa Maskavas olimpisko spēļu simbola lācīša figūra. Iekārtu "Lotoss", kas pašreiz atrodas Latvijas Ķīmijas vēstures muzeja krājumā, LPSR Zinātņu Akadēmijas Koksnes ķīmijas institūtā izstrādājis latviešu ķīmiķis, ķīmijas doktors, izgudrotājs un gleznotājs Arnolds Alksnis, un tā domāta polimerizācijas reakciju pētīšanai bezsvara stāvoklī.
Cambios en la frecuencia de los Regímenes de Tiempo sobre la región Euro-Atlántica y Mediterránea y su relación con las temperaturas anómalas sobre e…
2014
An exercise has been carried out to assess to what extent the Euro-Atlantic Weather Regimes (WR), described from the ERA-interim Reanalysis in the summer season, projects onto a pool of AGCMAMIP simulations in which sea surface temperatures (SST) are prescribed from observations. Although the model simulations present some biases in the spatial structure and seasonality of WRs, exhibiting also less variability, they are able to capture main WR over the region in summer season: +Middle East –Middle East, +NAO, -NAO. WR paradigm is used to quantify changes in the atmosphere under warmer/colder than normal conditions over the Mediterranean Sea. To address this problem, firstly, changes in the …
Impact of the Asian monsoon on the extratropical lower stratosphere: trace gas observations during TACTS over Europe 2012
2016
Abstract. The transport of air masses originating from the Asian monsoon anticyclone into the extratropical upper troposphere and lower stratosphere (Ex-UTLS) above potential temperatures Θ = 380 K was identified during the HALO aircraft mission TACTS in August and September 2012. In situ measurements of CO, O3 and N2O during TACTS flight 2 on 30 August 2012 show the irreversible mixing of aged stratospheric air masses with younger (recently transported from the troposphere) ones within the Ex-UTLS. Backward trajectories calculated with the trajectory module of CLaMS indicate that these tropospherically affected air masses originate from the Asian monsoon anticyclone. These air masses are …
Long-term changes in drought indices in eastern and central Europe
2021
This study analyses long-term changes in drought indices (Standardised Precipitation Index—SPI, Standardised Precipitation–Evapotranspiration Index—SPEI) at 1 and 3?months scales at 182 stations in 11 central and eastern European countries during 1949–2018. For comparative purposes, the necessary atmospheric evaporative demand (AED) to obtain SPEI was calculated using two methods, Hargreaves-Samani (SPEIH) and Penman-Monteith (SPEIP). The results show some relevant changes and tendencies in the drought indices. Statistically significant increase in SPI and SPEI during the cold season (November–March), reflecting precipitation increase, was found in the northern part of the study region, in …