Closest Meteorological Station Research Articles

Bathing water quality analysis, management and policy: an integrated assessment for Ireland

Abstract Every bathing season in Ireland several bathing sites are closing and receiving warnings against bathing. In this report, their water quality status is assessed, and the broader picture of each case is investigated. A database is formed including location-maps, the restrictions they were/are subject to, the official justification, past and current annual water quality status, (sub)catchment where they are located, main water bodies flowing in, the closest wastewater treatment plants with their characteristics and performance based on EU treatment standards, the closest meteorological stations and the rainfall data related with stormwater overflow events (correlation analyses) and the surrounding land cover. For each case, possible causes were discussed; the actions so far and the relevant literature are analyzed to provide key policy recommendations which are useful for the review of the European Bathing Water Directive.

Estimation of the Uncertainty due to Each Step of Simulating the Photovoltaic Conversion under Real Operating Conditions

The simulation of photovoltaic installations is a major issue for their sizing, their smart grid operation, and their fault detection and diagnosis. In this article, we study in detail every step of the simulation chain, either from the global horizontal irradiance and the ambient temperature (i.e., 4 steps of simulation) or considering the global in-plane irradiance and the module operating temperature (i.e., 1 step of simulation). The average quality estimation of the models is made through the calculations of average annual error between estimations and measurements, from 2016 to 2020. We have shown that the most uncertain step is the conversion of the global irradiance in its diffuse and direct components (17.2%, 2 models tested). If the model goes up to the in-plane irradiance, the average annual error decreases to 5.3% (6 models tested). The photovoltaic module temperature calculation induces an error of less than 2°C (4 models tested with 2 configurations). Meanwhile, the photoelectrical conversion shows a 3.5% error, similar to the measurement uncertainties, considering as input, the modules temperature, and the in-plane irradiance. If the simulation goes from the global irradiance and the ambient temperature measured locally, the estimation leads to a 6.7% average annual error. If the local measurements are not available, we can use the closest meteorological station’s records (13 for our study), and the error becomes 12.1%. Finally, we can also use the satellite images that lead to a 15.2% error, for average per year. The impact of available input shows that modeling the DC photovoltaic production, using global horizontal irradiance and ambient temperature, gives rise to an error of 6.6% for local measurements, 12.1% for weather station measurements, and 15.2% for satellite images estimations. This article thus draws up a review of the existing models, allowing to calculate the DC production of a photovoltaic module, depending on the atmospheric conditions, and highlights the most precise or most critical steps, considering in situ and weather station ground-based measurements, and also estimation from satellite images.

Effect of PM2.5 on circulating inflammatory cells and microRNA expression in acute coronary syndrome

Abstract Background Air pollutants increase the risk of myocardial infarction. Air pollution-induced atherosclerotic plaque destabilization may be related to inflammation, but the specific inflammatory alterations remain unclear. Purpose The aim of this prospective study was to assess the inflammatory changes in circulating immune cells and microRNAs in patients with acute coronary syndrome related to short-term exposure to PM2.5. Methods We prospectively included all consecutive patients admitted between March 2017 and July 2018 with the diagnosis of acute coronary syndrome (STEMI, NSTEMI, unstable angina) and coronary angiography in the acute phase of the disease. We also included a control group of patients with stable angina. For each patient we collected air concentrations of PM2.5 from the closest meteorological station to the patient residence obtaining the previous 24-hour average before hospital admission. All patients underwent systematic circulating inflammatory cell analysis. A selection of patients underwent miRNAs analysis. Results A total of 261 patients were included. According to PM2.5 exposure, 31 patients were selected for miRNA analyses. STEMI patients exposed to PM2.5 showed a reduction of CD4+ regulatory T (Treg) cells (Figure 1A). In the microRNA assessment, PM2.5 exposure was associated with higher circulating levels of let-7f-5p, miR-223-3p, miR-423-3p, miR-197-3p, miR-335–5, miR-376c-3p and miR-501-3p. Regarding clinical presentation, PM2.5 exposure in STEMI and NSTEMI patients was associated with an increase of miR-let-7f-5p, whereas miR-423-3p and miR-146a-5p were increased only in STEMI patients (Figure 1B). Conclusions STEMI related to PM2.5 short-term exposure is associated to specific changes involving CD4+CD25+Foxp3+ Treg cells and miR-146a-5p. Funding Acknowledgement Type of funding sources: Other. Main funding source(s): Ministerio de Ciencia e Innovaciόn; Fundaciόn BBVA Equipos de Investigaciόn Científica 2018 and from Caixa Banking Foundation; Sociedad Espanola de Cardiologia; Ministerio de Ciencia, Innovaciόn y Universidades, Carlos III Institute of Health-Fondo de Investigaciόn Sanitaria; Comunidad de Madrid; Fondo Europeo de Desarrollo Regional

Climatic influence on the risk of abdominal aortic aneurysm rupture.

Our aim is to examine the effects of climatic conditions on the incidence of ruptured abdominal aortic aneurysms (rAAA) in Catalonia, Spain. We combined clinical data from the Public Health official registries in Catalonia, Spain (HD-MBDS) of all rAAA with local climatic data obtained from the closest meteorological station (69 stations, National Meteorological Service: MeteoCat) from 2008 to 2017. We analyzed the median, maximum, minimum, and variability of atmospheric pressure (hPa) and air temperature (°C), solar irradiation (MJ/m2), humidity (%), accumulated precipitation (mm), median wind, and maximum flaw direction and velocity (°, m/s), recorded on the days of events, the previous day, and mean results for 3, 7, and 30 days before, as well as seasonality. Seventy-five control days were randomly selected in a 1-year period around every rAAA day at the same meteorological station, and compared. A total of 717 days and locations with rAAA were identified, and 53,775 controls were randomly selected. For the rAAA days, there were significantly lower temperatures, lower solar global irradiation, and higher mean humidity levels in all time periods (p < 0.001, p < 0.001, p < 0.05); higher atmospheric pressure variability during 1 week and 1 month before (p = 0.011, p = 0.007); and they often occurred during autumn/winter (57.6%, p < 0.001). Logistic regression identified low mean temperatures on the days of ruptures and high mean humidity the week before as independent rupture predictors. In conclusion, low median temperatures the same day and high humidity during 1 week before were identified as independent predictors of rAAA occurrence. The role of climate on pathophysiologic mechanisms may require further investigation.

Weather Radar Data for Hydrological Modelling: An Application for South of Primorye Region, Russia

This paper describes the experience of using weather radar data to simulate a catastrophic flood caused by intense rains that occurred in the period from August 5 to 8, 2017 in the south of Primorye, Russia. The Amba River (243 km²), where historical discharge peak was measured, was chosen as the test watershed of this study. Weather radar hourly precipitation fields with a spatial resolution of 1 km and a modified version of the kinematic-wave-based geomorphologic IUH model were used to estimate the hydrograph at the watershed outlet. The simulation was performed with an hourly time step; using the precipitation grids obtained from initial radar reflectivity data, and then using bias-correction based on precipitation measurement at the closest meteorological station. In the preliminary tests, the simulated discharge was found underestimated about two times in comparison with the observed discharges. After performing a precipitation bias-correction, the simulated and observed discharges showed good accordance.

Testing A Methodology to Assess Fluctuations of Coastal Rocks Surface Temperature

The aim of this work is testing a cheap and user-friendly methodology suitable for studying temperature fluctuations of coastal rocks’ surfaces. An infrared thermometer was used, that permits a contactless measurement of the average surface temperature of a patch around a measuring point. Temperature was measured in an array of selected plots every 45 min from dawn to sunset in a 20 m2 study area along the rocky coast of Calafuria (NW Italy). During the experiment daily temperature in all plots was minimum at dawn and quickly reached its peak value shortly after sun culmination; subsequently, it underwent a small-gradient decrease until sunset. In connection with temporary sun-shading and wind gusts relevant short-term rock surface temperature fluctuations were recorded. Considering mean daily temperature in each plot, it proved to be positively correlated with distance from the shoreline. As regards daily temperature range, its amplitude progressively increased moving farther from the shoreline. The measuring points located where the rock is extensively covered by barnacles experience a temperature magnification effect, possibly due to a micro-greenhouse effect triggered by the production of carbon dioxide by this biota. The entity of measured daily temperature fluctuations is ca. one order of magnitude greater than air temperature fluctuations measured at the same elevation in the closest meteorological station. The results of this work highlight that the infrared thermometer is an effective tool to measure rock surface temperature along rocky coasts, capable of detecting temperature fluctuations more effectively than traditionally employed data loggers. Moreover, this work emphasizes the relevance of temporary sun-shading and wind gusts in triggering short-term rock surface temperature fluctuations, potentially capable of enhancing thermal fatigue and foster surface rock breakdown.

FORECASTING MISSING DATA USING DIFFERENT METHODS FOR ROAD MAINTAINERS

Observations collected from meteorological stations that are available to road maintainers and used for experimental purposes in this paper. Unfortunately, these observations are insufficient to make good forecasting that is needed for road maintainers. Those meteorological stations are located next to the road surface in the territory of the Republic of Latvia. The road maintainers can make forecasting using this data what is needed for the winter months. It is up to the road maintainers in winter months to process decision-making on road surface smudging with anti-slip chemical materials. The missing data in each meteorological station exists from time to time. The paper represents the possibility of using several approaches to fill out these missing data. This process is needed to be more accurate in predicting specific parameters aggregated from meteorological stations. These approaches are compared between the three closest meteorological stations available in the Republic of Latvia. The relevant data are for the winter months of 2017-2018. To conclude which is more accurate with VAS "Latvijas valsts celi" data set.

Empirical test of the ClimateWNA model for local accuracy in the Kluane Lake area of the southern Yukon, Canada

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 75:111-115 (2018) - DOI: https://doi.org/10.3354/cr01511 NOTE Empirical test of the ClimateWNA model for local accuracy in the Kluane Lake area of the southern Yukon, Canada Charles J. Krebs1,*, J. David Henry2, Alice J. Kenney1, Elizabeth J. Hofer1 1Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver BC V6T 1Z4, Canada 2Kluane National Park and Reserve, Parks Canada, Haines Junction YT Y0B 1L0, Canada *Corresponding author: krebs@zoology.ubc.ca ABSTRACT: Ecological studies related to climate typically require data on temperature and rainfall. If local climate data are not available, the only recourse is to rely on data from the closest meteorological station or interpolated data from regional models of climate. In the southwestern Yukon, we have for the past 25 yr gathered ecological information such as counts of cones on white spruce trees and attempted to relate these biological variables to weather variables, thus requiring accurate climate information. From 2001 to 2014, we measured local summer temperature and rainfall during the growing season at 7 local sites along 250 km of the Alaska Highway and tested the accuracy of the ClimateWNA model estimates for these 7 sites as well as for the Haines Junction Environment Canada meteorological station. Monthly summer temperatures were reasonably well correlated with the predicted ClimateWNA values (r = 0.90, n = 299 mo), but summer rainfall was not (r = 0.37, n = 218 mo). We repeated this analysis with the Daymet climate model and got similar results. We caution the use of ClimateWNA or Daymet rainfall estimates for local areas in this part of the southwestern Yukon for the prediction of ecological measurements. KEY WORDS: ClimateWNA · Daymet · Temperature · Rainfall · Kluane · Yukon · Accuracy Full text in pdf format PreviousNextCite this article as: Krebs CJ, Henry JD, Kenney AJ, Hofer EJ (2018) Empirical test of the ClimateWNA model for local accuracy in the Kluane Lake area of the southern Yukon, Canada. Clim Res 75:111-115. https://doi.org/10.3354/cr01511 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 75, No. 2. Online publication date: May 17, 2018 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2018 Inter-Research.

Apparent performance ratio of photovoltaic systems—A methodology for evaluation of photovoltaic systems across a region

Most of the photovoltaic (PV) solar systems track none or only basic monitoring data, thus the investor has no or limited information about the performance, quality, and reliability of a PV system. In this paper, we report on a methodology to evaluate a large number of PV systems on a regional or even countrywide level. The methodology is based on an apparent performance ratio, a factor close to the temperature compensated performance ratio, although based on solar irradiation data from the closest meteorological station. The methodology is compared to a more detailed evaluation procedure and a comprehensive evaluation of a PV system where all the required—both electrical and meteorological—data are monitored. The results confirm that the apparent performance ratio is very similar to the temperature compensated performance ratio of a PV system.

Features of change of permanent snow patches in the Mongun-Taiga Massif, 1966–2011

The article is dedicated to perennial snow patches of Mongun-Taiga mountain massif (south-western Tuva), their morphology, present state and dynamics over the last 45 years. We created a scheme of snow patch classification with regard to genesis of relief and position on the slopes. Dynamics of snow patches is analyzed for periods between several time points – 1966 (on basis of aerial photos), 2000, 2007–2008 and 2011 (on basis of field measurements and observations). From 1966 to 2008 the number of snow patches decreased by 4 times, the total area – by 15 times, the altitudinal zone of snow patches moved 250–300 m up. In 2008–2011 the altitudinal zone of snow patches partly recovered, its lower limit moved 250 m down, periglacial snow patches recovered, a new type – snow patches of buried ice and debris-covered glaciers appeared. It could be the first face of the process of small glaciers recovery in the massif. Using the changes of the altitudinal position of snow patches in comparison with data of the closest meteorological station we estimated the amount of annual precipitation, critical for the existence of local snow patches.

Remote Sensing Data in Wind Velocity Field Modelling: a Case Study from the Sudetes (SW Poland)

The phenomena of wind-field deformation above complex (mountainous) terrain is a popular subject of research related to numerical modelling using GIS techniques. This type of modelling requires, as input data, information on terrain roughness and a digital terrain/elevation model. This information may be provided by remote sensing data. Consequently, its accuracy and spatial resolution may affect the results of modelling. This paper represents an attempt to conduct wind-field modelling in the area of the Śnieżnik Massif (Eastern Sudetes). The modelling process was conducted in WindStation 2.0.10 software (using the computable fluid dynamics solver Canyon). Two different elevation models were used: the Global Land Survey Digital Elevation Model (GLS DEM) and Digital Terrain Elevation Data (DTED) Level 2. The terrain roughness raster was generated on the basis of Corine Land Cover 2006 (CLC 2006) data. The output data were post-processed in ArcInfo 9.3.1 software to achieve a high-quality cartographic presentation. Experimental modelling was conducted for situations from 26 November 2011, 25 May 2012, and 26 May 2012, based on a limited number of field measurements and using parameters of the atmosphere boundary layer derived from the aerological surveys provided by the closest meteorological stations. The model was run in a 100-m and 250-m spatial resolution. In order to verify the model’s performance, leave-one-out cross-validation was used. The calculated indices allowed for a comparison with results of former studies pertaining to WindStation’s performance. The experiment demonstrated very subtle differences between results in using DTED or GLS DEM elevation data. Additionally, CLC 2006 roughness data provided more noticeable improvements in the model’s performance, but only in the resolution corresponding to the original roughness data. The best input data configuration resulted in the following mean values of error measure: root mean squared error of velocity = 1.0 m/s and mean absolute error of direction = 30°. The author concludes that, within specific meteorological conditions (relatively strong and constant synoptic forcing) and using the aforementioned input data, the Canyon model provides fairly acceptable results. Similarly, the quality of the presented remote sensing data is suitable for wind velocity modelling in the proposed resolution. However, CLC 2006 land use data should be first verified with a higher-resolution satellite or aerial imagery.

Stable carbon isotopes from Torneträsk, northern Sweden provide a millennial length reconstruction of summer sunshine and its relationship to Arctic circulation

This paper presents results from the first 1100 years of a long stable carbon isotope chronology currently in development from Scots Pine (Pinus sylvestris L.) trees growing in the Torneträsk region of northern Sweden. The isotope record currently comprises a total of 74 trees with a mean annual replication of >12, thereby enabling it to be compared directly with other tree-ring based palæoclimate reconstructions from this region. In developing the reconstruction, several key topics in isotope dendroclimatology (chronology construction, replication, CO2 adjustment and age trends) were addressed.The resulting carbon isotope series is calibrated against instrumental data from the closest meteorological station at Abisko (AD1913–2008) to provide a record of June–August sunshine for northern Fennoscandia. This parameter is closely linked to the direct control of assimilation rate; Photosynthetically Active Radiation (PAR) and the indirect measures; mean July–August temperature and percent cloud cover. The coupled response of summer sunshine and temperature in this region permits a multi-parameter comparison with a local reconstruction of past temperature variability based upon tree growth proxies to explore the stability of this coupling through time.Several periods are identified where the temperature (X-ray density) and sunshine (stable carbon isotope ratio) records diverge. The most significant and sustained of these occur between c AD1200–1380 and c AD1550–1780, providing evidence for a cool, sunny, two-phase “Little Ice Age”. Whilst summer sunshine reconstructed for the 20th century is significantly different from the mean of the last 1100 years (P < 0.01), conditions during the early mediæval period are similar to those experienced in northern Fennoscandia during the 20th century (P > 0.01), so it is the 17th–18th, and to a lesser extent, the 13th centuries rather than the early mediæval period that appear anomalous when viewed within the context of the last 1100 years. The observed departures between temperature and sunshine are interpreted as indicating a change in large-scale circulation associated with a southward migration of the Polar Front. Such a change, affecting the Northern Annular Mode (Arctic Oscillation) would result in more stable anticyclonic conditions (cool, bright, summers) over northern Fennoscandia, thus providing a testable mechanism for the development of a multi-phase, time-transgressive “Little Ice Age” across Europe.

Relationships between MODIS and ATSR fires and atmospheric variability in New Caledonia (SW Pacific)

[1] We examined the relationships between fires detected by the Along Track Scanning Radiometer, algorithm 2 (ATSR-2) and the Moderate Resolution Imaging Spectrometer (MODIS) sensors and local-scale atmospheric conditions in New Caledonia (SW Pacific ∼165.5°E, 21.5°S) during the 1996–2008 (ATSR) and 2000–2008 (MODIS) time periods. A total of 3707 (MODIS) hotspots, representing 949 distinct fires, and 83 (ATSR) hotspots were observed during the study period. The annual mean frequency of hotspots peaks around the transition between the dry-cool season and the wet-warm season, that is, in September–December, when dry soils and fuels could be combined with increasing temperatures. The antecedent local-scale maximum temperature and rainfall anomalies recorded at the closest meteorological station were analyzed. While the signal in maximum temperature is weak and not robust among the fire records, the local-scale anomalies of rainfall are always clearly negative for at least 3 months before the fires (i.e., between June and December). The Effective Drought Index (EDI), based on rainfall only, and the Fire Weather Index (FWI), which combines rainfall, temperature, relative humidity, and wind speed, show similar behaviors before fires. This suggests that a simple rainfall index, as well as a more comprehensive one, is able to diagnose fire risks. At interannual time scale, cross-correlation analysis reveals that the seasonal June–August Nino 3.4 sea surface temperature index is strongly correlated (r = 0.78 for a second-order polynomial fit) with the monthly frequency of all MODIS hotspots in September–December, suggesting a strong potential predictability of fire variations in New Caledonia with a lead time of 1–4 months.

Chironomid-inferred temperature changes of the last century in anoxic Seebergsee, Switzerland: assessment of two calibration methods

Chironomids (non-biting midges) can provide accurate climate reconstructions from the Late Glacial to the present. Until now, anoxic lakes have been avoided for temperature reconstructions since chironomid assemblages are sensitive to changes in oxygen concentrations in the hypolimnion. However, anoxic lakes may have varved sediments, providing the possibility for near-annual climate reconstructions. Here, we tested the applicability of two calibration methods to reconstruct mean July air temperatures from chironomid assemblages preserved in the sediments of the anoxic Seebergsee located in the northern Swiss Alps: a calibration-in-space approach and a calibration-in-time approach. The calibration-in-space approach (i.e. chironomid assemblages from surficial lake sediments (0–1 cm) calibrated against meteorological data) provided accurate inferences (i.e. similar temperature changes as measured at the closest meteorological station, and at regional stations) in the Seebergsee stratigraphy until anoxia increased in the lake. With the increase of anoxia, the chironomid-inferred temperatures were generally colder than measured temperatures. A calibration-in-time approach (i.e. calibration of chironomid assemblages in a time series against instrumental data from the closest meteorological station) provided accurate reconstructions (i.e. similar to the regional records) for the past 100 years, including the time period of inferred anoxia. However, its applicability should be further tested on longer temporal scales.

New perspectives on the synoptic and mesoscale structure of Hurricane Catarina

This work explores in detail synoptic and mesoscale features of Hurricane Catarina during its life cycle from a decaying baroclinic wave to a tropical depression that underwent tropical transition (TT) and finally to a Category 2 hurricane at landfall over Santa Catarina State coast, southern Brazil. This unique system caused 11 deaths mostly off the Brazilian coast and an estimated half billion dollars in damage in a matter of a few hours on 28 March 2004. Although the closest meteorological station available was tens of kilometres away from the eye, in situ meteorological measurements provided by a work-team sent to the area where the eye made landfall unequivocally reproduces the tropical signature with category 2 strength, adding to previous analysis where this data was not available. Further analyses are based mostly on remote sensing data available at the time of the event. A classic dipole blocking set synoptic conditions for Hurricane Catarina to develop, dynamically contributing to the low wind shear observed. On the other hand, on its westward transit, large scale subsidence limited its strength and vertical development. Catarina had relatively cool SST conditions, but this was mitigated by favourable air–sea fluxes leading to latent heat release-driven processes during the mature phase. The ocean's dynamic topography also suggested the presence of nearby warm core rings which may have facilitated the transition and post-transition intensification. Since there were no records of such a system at least in the past 30 years and given that SSTs were generally below 26 °C and vertical shear was usually strong, despite all satellite data available, the system was initially classified as an extratropical cyclone. Here we hypothesise that this categorization was based on inadequate regional scale model outputs which did not account for the importance of the latent heat fluxes over the ocean. Hurricane Catarina represents a dramatic event on weather systems in South America. It has attracted attention worldwide and poses questions as whether or not it is a symptom of global warming.

Estimation of Actual Evapotranspiration by Remote Sensing: Application in Thessaly Plain, Greece.

Remote sensing can assist in improving the estimation of the geographical distribution of evapotranspiration, and consequently water demand in large cultivated areas for irrigation purposes and sustainable water resources management. In the direction of these objectives, the daily actual evapotranspiration was calculated in this study during the summer season of 2001 over the Thessaly plain in Greece, a wide irrigated area of great agricultural importance. Three different methods were adapted and applied: the remote-sensing methods by Granger (2000) and Carlson and Buffum (1989) that use satellite data in conjunction with ground meteorological measurements and an adapted FAO (Food and Agriculture Organisation) Penman-Monteith method (Allen at al. 1998), which was selected to be the reference method. The satellite data were used in conjunction with ground data collected on the three closest meteorological stations. All three methods, exploit visible channels 1 and 2 and infrared channels 4 and 5 of NOAA-AVHRR (National Oceanic and Atmospheric Administration - Advanced Very High Resolution Radiometer) sensor images to calculate albedo and NDVI (Normalised Difference Vegetation Index), as well as surface temperatures. The FAO Penman-Monteith and the Granger method have used exclusively NOAA-15 satellite images to obtain mean surface temperatures. For the Carlson-Buffum method a combination of NOAA-14 and NOAA-15 satellite images was used, since the average rate of surface temperature rise during the morning was required. The resulting estimations show that both the Carlson-Buffum and Granger methods follow in general the variations of the reference FAO Penman-Monteith method. Both methods have potential for estimating the spatial distribution of evapotranspiration, whereby the degree of the relative agreement with the reference FAO Penman-Monteith method depends on the crop growth stage. In particular, the Carlson-Buffum method performed better during the first half of the crop development stage, while the Granger method performed better during the remaining of the development stage and the entire maturing stage. The parameter that influences the estimations significantly is the wind speed whose high values result in high underestimates of evapotranspiration. Thus, it should be studied further in future.

Development of a sky imager for cloud cover assessment

Based on a CCD camera, we have developed an in-house sky imager system for the purpose of cloud cover estimation and characterization. The system captures a multispectral image every 5 min, and the analysis is done with a method based on an optimized neural network classification procedure and a genetic algorithm. The method discriminates between clear sky and two cloud classes: opaque and thin clouds. It also divides the image into sectors and finds the percentage of clouds in those different regions. We have validated the classification algorithm on two levels: image level, using the cloud observations included in the METAR register performed at the closest meteorological station, and pixel level, determining whether the final classification is correct.

Water balance investigations in Svalbard

This paper reviews and summarizes all known previous water balance studies in Svalbard. An updated water balance computation was then done for the three water catchments with the best data: Bayelva, De Geerdalen and Isdammen/Endalen for 10 hydrological years 1990-2001. The computations were based on the best available data and correction methods. Special emphasis was put on correction of precipitation data, both for catch errors and gradients in precipitation. Areal precipitation in the three catchments is more than two times the measured precipitation at the closest meteorological station: 548 mm/year in De Geerdalen, 486 mm/year in Endalen/Isdammen and 890 mm/year in Bayelva. Compared to this, average measured precipitation is only 199 mm/year at Svalbard Airport, close to Endalen/Isdammen and De Geerdalen, and 426 mm/year in Ny-Alesund, close to Bayelva. Evaporation is not well understood in Svalbard; the best estimates indicate an average annual evaporation of ca. 80 mm/year from glacier-free areas, and no net evaporation from glaciers. Glacial mass balance has in general been negative in Svalbard during the last 40 years, leading to a significant contribution to the water balance, on the order of 450 mm/year on average. Annual runoff ranges from 545 mm in Endalen/Isdammen, 539 mm/year in De Geerdalen up to 1050 mm/year in Bayelva. Runoff computed from water balance compares well with observed runoff, and average error in water balance is less than ±30 mm/year in all three catchments.

Water balance investigations in Svalbard

This paper reviews and summarizes all known previous water balance studies in Svalbard. An updated water balance computation was then done for the three water catchments with the best data: Bayelva, De Geerdalen and Isdammen/Endalen for 10 hydrological years 1990-2001. The computations were based on the best available data and correction methods. Special emphasis was put on correction of precipitation data, both for catch errors and gradients in precipitation. Areal precipitation in the three catchments is more than two times the measured precipitation at the closest meteorological station: 548 mm/year in De Geerdalen, 486 mm/year in Endalen/Isdammen and 890 mm/year in Bayelva. Compared to this, average measured precipitation is only 199 mm/year at Svalbard Airport, close to Endalen/Isdammen and De Geerdalen, and 426 mm/year in Ny-Ålesund, close to Bayelva. Evaporation is not well understood in Svalbard; the best estimates indicate an average annual evaporation of ca. 80 mm/year from glacier-free areas, and no net evaporation from glaciers. Glacial mass balance has in general been negative in Svalbard during the last 40 years, leading to a significant contribution to the water balance, on the order of 450 mm/year on average. Annual runoff ranges from 545 mm in Endalen/Isdammen, 539 mm/year in De Geerdalen up to 1050 mm/year in Bayelva. Runoff computed from water balance compares well with observed runoff, and average error in water balance is less than ±30 mm/year in all three catchments.

Climatological significance of δ18O in north Tibetan ice cores

Oxygen isotopic ratios (δ18O) of precipitation samples collected over several years at three meteorological stations on the northern Tibetan Plateau were used to conduct the first investigation of the relationship between δ18O and contemporaneous air temperatures (Ta). Inferring past temperatures from δ18O measured in recently acquired Tibetan ice cores necessitates establishing whether a δ18O‐Ta relationship exists. For each station a strong temporal relationship is found between δ18O and Ta, particularly for monthly averages which remove synoptic‐scale influences such as changes in condensation level, condensation temperature, and moisture sources. Moisture source is identified as a major factor in the spatial distribution of δ18O, but air temperature determines the temporal fluctuations of δ18O at individual sites on the northern Tibetan Plateau. The 30‐year records of annually averaged δ18O from three different ice coring sites are not correlated significantly with contemporaneous air temperature records from their closest meteorological station (150 to 200 km). However, since 1960 the three air temperature records reveal a modest warming trend, while the three contemporaneous δ18O records show a modest 18O enrichment.