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1.
Ground-based measurements are essential for understanding alpine glacier dynamics, especially in remote regions where in-situ measurements are extremely limited. From 1 May to 22 July 2005 (the spring-summer period), and from 2 October 2007 to 20 January 2008 (the autumn-winter period), surface radiation as well as meteorological variables were measured over the accumulation zone on the East Rongbuk Glacier of Mt. Qomolangma/Everest at an elevation of 6560 m a.s.l. by using an automatic weather station (AWS). The results show that surface meteorological and radiative characteristics were controlled by two major synoptic circulation regimes: the southwesterly Indian monsoon regime in summer and the westerlies in winter. At the AWS site on the East Rongbuk Glacier, north or northwest winds prevailed with high wind speed (up to 35 m s-1 in January) in winter while south or southeast winds predominated after the onset of the southwesterly Indian monsoon with relatively low wind speed in summer. Intensity of incoming shortwave radiation was extremely high due to the high elevation, multiple reflections between the snow/ice surface and clouds, and the high reflective surrounding surface. These factors also caused the observed 10-min mean solar radiation fluxes around local noon to be frequently higher than the solar constant from May to July 2005. The mean surface albedo ranged from 0.72 during the spring-summer period to 0.69 during the autumn-winter period. The atmospheric incoming longwave radiation was greatly affected by the cloud condition and atmospheric moisture content. The overall impact of clouds on the net all-wave radiation balance was negative in the Mt. Qomolangma region. The daily mean net all-wave radiation was positive during the entire spring-summer period and mostly positive during the autumn-winter period except for a few overcast days. On monthly basis, the net all-wave radiation was always positive.  相似文献   

2.
An analysis of the periodicities found in the Nimbus-7 satellite measurements of solar irradiance (Solar Constant) indicates variations on three scales. Two of these variations are shown to be related to variations in solar activity as given by various indicators of solar photosphere disturbances. The high frequency periodicity is due to the solar rotation period. The second periodicity is based on the integral effect of the high frequency oscillation over an 11 year solar cycle. The third variation (secular trend) is discussed in regard to the high precision cavity data and the recent record of high altitude solar constant measurements.  相似文献   

3.
Summary During two measurement campaigns in 1992 (the Hartheim Experiment HartX- and an additional experiment in autumn), measurements of soil moisture were carried out in aPinus sylvestris stand at Hartheim on the Oberrhein. Several methods were used to determine soil water status. They were compared in terms of suitability for estimating stand evapotranspiration (ET) via soil water depletion. Measurements of tree water potential suggested that conductance of the trees was affected by soil water depletion during the period of the HartX campaign in spring 1992. We interpret the observations to indicate a lesser influence of soil water availability on tree transpiration during the autumn experiment.Eddy correlation and xylem sapflow measurements provided reference ET values with which to compare the stand ET calculations based on soil moisture measurements. Profile measurements of soil moisture showed that particularly in springtime when the lower soil layers are saturated with water, the water transport from depths below the major rooting zone is a very important factor affecting evaluation of stand ET. Decreases in soil water storage may be determined best with permanently installed soil moisture sensors such as used in tensiometric or TDR measurements that provide high resolution of changes over time.With 8 Figures  相似文献   

4.
Precipitation and evaporation budgets over the Baltic Sea were studied in a concerted project called PEP in BALTEX (Pilot study of Evaporation and Precipitation in the Baltic Sea), combining extensive field measurements and modelling efforts. Eddy-correlation-measurements of turbulent heat flux were made on a semi-continuous basis for a 12 month period at four well-exposed coastal sites in the Baltic Proper (the main basin of the Baltic Sea). Precipitation was measured at land-based sites with standard gauges and on four merchant ships travelling between Germany and Finland with the aid of specially designed ship rain gauges (SRGs). The evaporation and precipitation regime of the Baltic Sea was modelled for a 12 month period by applying a wide range of numerical models: the operational atmospheric High Resolution Limited Area Model (HIRLAM, Swedish and Finnish versions), the German atmospheric REgional-scale MOdel, REMO, the operational German Europe Model (only precipitation), the oceanographic model PROBE-Baltic, and two models that use interpolation of ground-based data, the Swedish MESAN model of SMHI and a German model of IFM-GEOMAR Kiel. Modelled precipitation was compared with SRG measurements on board the ships. A reasonable correlation was obtained, but the regional-scale models and MESAN gave some 20% higher precipitation over the sea than is measured. Bulk parameterisation schemes for evaporation were evaluated against measurements. A constant value of CHN and CEN with wind speed, underestimated large fluxes of both sensible and latent heat flux. The limited area models do not resolve the influence of the height of the marine boundary layer in coastal zones and the entrainment (on the surface fluxes), which may explain the observed low correlations between modelled and measured latent heat fluxes. Estimates of evaporation, E, and precipitation, P, for the entire Baltic Proper were made with several models for a 12 month period. While the annual variation was well represented by all predictions, there are still important differences in the annual means. Evaporation ranges from 509 to 625 mm year-1 and precipitation between 624 and 805 mm year-1 for this particular 12 month period. Taking the results of model verification from the present study into account, the best estimate of P-E is about 100 ± 50 mm for this particular 12 month period. But the annual mean of P-E varies considerably from year to year. This is reflected in simulations with the PROBE-Baltic model for an 18 year period, which gave 95 mm year-1 for the 12 month period studied here and 32 mm year-1 as an average for 18 years.  相似文献   

5.
In this paper, a modern techniqne for correction of precipitation measured with a Nipher shielded rain gauge, with the use of the Valdai Control System as an intercomparison reference, is presented. This technique allows obtaining unbiased daily and timed precipitation data not affected by the rain gauge systematic errors. In conjunction with the existing method of the bias correction for precipitation measured with the Tretyakov precipitation gauge, the problem of generation of unbiased precipitation time series, which includes both types of measurements, covers the entire period of measurements, and has any (i.e., daily through yearly) temporal resolution, is solved. The results of correction for nine stations located in different climatic zones of the Russian Federation are shown. The results are summarized and presented in the form of long-term averages. Statistically homogeneous precipitation time series for the period from 1936 to 2000 are obtained. Temporal trends of annual and cold-season precipitation are calculated and analysed, and their statistical significance is estimated.  相似文献   

6.
NASA/GEWEX (National Aeronautics and Space Administration/Global Energy and Water Cycle Experiment) Surface Radiation Budget (SRB) has released its latest radiation dataset, version 3.0. We examine the accuracy of the monthly mean global radiation in China using surface-observed radiation (SOR) data at 42 stations during the period 1984?C2004. Overall comparison shows a general overestimation of satellite retrieval radiation data with a bias of 14.6?W?m?2 and a root mean square error of 25.9?W?m?2. Differences at individual stations suggested satellite data are consistently higher than surface measurements over eastern China (110°E), but occasional underestimation occurs in Western China, especially Southwest China. Intra-annual variation analysis indicates that SRB satellite radiation can capture the annual cycle well. For trend of global radiations, there are evident discrepancies between satellite retrievals and surface measurements for both the entire period and segmental terms. For the entire period from 1984 to 2004, most stations show a positive trend based on surface measurements, while the majority of collocated pixels show a negative trend. Segmental trends demonstrated that the principal difference occurred during the first period of 1981?C1994. After 1994, the two datasets change similarly. Therefore, trend analysis in terms of detecting global dimming/brightening remains very difficult as surface measurements and satellite products do not agree yet. In addition, some proposals are made towards better understanding of the bias of satellite products and to improve further the satellite retrieval algorithm with better representation of both cloud and aerosol properties.  相似文献   

7.
Presented are the results of measurements of air temperature, wind direction, and relative humidity of the air at the high-altitude meteorological mast in the town of Obninsk. The measurements were carried out in the period of hot weather in July?CAugust 2010 near the Earth??s surface, as well as at the heights of 121 and 301 m. The wind roses and maximum daily temperatures are compared with the similar climatic characteristics obtained for the period of 1970?C2009. It is shown that the period from July 15 to August 18, 2010 was abnormal both in the air temperature characteristics and in the distribution of wind direction at all mentioned heights.  相似文献   

8.
Phase Two of the Integrative Monsoon Frontal Rainfall Experiment(IMFRE-II)was conducted over the middle and lower reaches of the Yangtze River during the period 16 June to 19 July 2020.This paper provides a brief overview of the IMFRE-II field campaign,including the multiple ground-based remote sensors,aircraft probes,and their corresponding measurements during the 2020 mei-yu period,as well as how to use these numerous datasets to answer scientific questions.The highlights of IMFRE-II are:(1)to the best of our knowledge,IMFRE-II is the first field campaign in China to use ground-based,airborne,and spaceborne platforms to conduct comprehensive observations over the middle and lower reaches of the Yangtze River;and(2)seven aircraft flights were successfully carried out,and the spectra of ice particles,cloud droplets,and raindrops at different altitudes were obtained.These in-situ measurements will provide a“cloud truth”to validate the ground-based and satellite-retrieved cloud and precipitation properties and quantitatively estimate their retrieval uncertainties.They are also crucial for the development of a warm(and/or cold)rain conceptual model in order to better understand the cloud-to-rain conversion and accretion processes in mei-yu precipitation events.Through an integrative analysis of ground-based,aircraft,and satellite observations and model simulations,we can significantly improve our cloud and precipitation retrieval algorithms,investigate the microphysical properties of cloud and precipitation,understand in-depth the formation and dissipation mechanisms of mei-yu frontal systems,and improve cloud microphysics parameterization schemes and model simulations.  相似文献   

9.
In this paper, a statistical analysis on wind and wave buoy measurements and wind and wave model forecasts obtained during a two-year period (1999-2001) is presented with reference to four characteristic near-shore sites of the Aegean Sea. The measurements are a main product of the "POSEIDON" system aiming at the monitoring and forecasting of the state of the Greek seas, operated by the National Centre for Marine Research (NCMR). Although the two-year period is rather short for a thorough analysis of the local wind and wave climate, yet the obtained results, presented herein for the first time, reveal some interesting features of the corresponding wave and wind characteristics. Comparisons between the measurements and the forecast results are also performed at the locations under consideration. It is found that (i) wind speeds obtained from the POSEIDON weather forecasting system are, in general, in agreement with the measurements, except for high wind speeds which are systematically underestimated, (ii) the WAM model can successfully follow the monthly and over year trend of the evolution of wind and wave characteristics, but face significant problems for efficient sea-state forecasting. Finally, the overall pattern of the wind/wave climate for the entire Aegean Sea as obtained from the models is presented by means of the spatial distribution of the mean annual wind and sea-state intensity.  相似文献   

10.
The next generation Geostationary Operational Environmental Satellite-R series (GOES-R) Advanced Baseline Imager (ABI) legacy atmospheric profile (LAP) retrieval algorithm is applied to the Advanced Himawari Imager (AHI) radiance measurements from the Himawari-8 satellite. Derived products included atmospheric temperature/moisture profiles, total precipitable water (TPW), and atmospheric stability indices. Since both AHI and ABI have 9 similar infrared bands, the GOES-R ABI LAP retrieval algorithm can be applied to the AHI measurements with minimal modifications. With the capability of frequent (10-min interval) full disk observations over the East Asia and Western Pacific regions, the AHI measurements are used to investigate the atmospheric temporal variation in the pre-landfall environment for typhoon Nangka (2015). Before its landfall over Japan, heavy rainfalls from Nangka occurred over the southern region of Honshu Island. During the pre-landfall period, the trends of the AHI LAP products indicated the development of the atmospheric environment favorable for heavy rainfall. Even though, the AHI LAP products are generated only in the clear skies, the 10-minute interval AHI measurements provide detailed information on the pre-landfall environment for typhoon Nangka. This study shows the capability of the AHI radiance measurements, together with the derived products, for depicting the detailed temporal features of the pre-landfall environment of a typhoon, which may also be possible for hurricanes and storms with ABI on the GOES-R satellite.  相似文献   

11.
Abstract

Since 1969, meteorological and limnological measurements required for evaporation estimates by the energy budget method have been made almost continuously during the open water season at Perch Lake, a small (0.45 km2), shallow (mean depth 2 m) lake on the Canadian Shield. Hydrological measurements required for water budget calculations have been made continuously since 1970. Since ground water input to the lake has been found to be significant, energy budget estimates of evaporation are used in the water budget equation to estimate ground water inflow. Results are summarized as the long‐term averages along with the ranges of variation of the budget components observed during the eleven‐year period.  相似文献   

12.
Based on the AIRS satellite spectrometer data (the Aqua platform), the peculiarities are studied of the field of total ozone (TO) under prolonged blocking conditions over the European part of Russia in summer 2010. It is revealed that the spatial distribution of TO values during the period of blocking was characterized by negative TO anomalies (up to -37 DU on the first ten days of August) over the western and northern peripheries of the blocking anticyclone and by positive TO anomalies (up to 60 DU) over the troughs adj oinmg the anticyclone. Possible mechanisms of the formation of TO anomalies are discussed. The results are presented of the validation of TO measurements with the AIRS spectrometer in May-September 2010 obtained from the data of TO measurements with Brewer spectrophotometers at Kislovodsk and Obninsk stations of the global ozone network.  相似文献   

13.
Summary During the ALPEX SOP (March–April, 1982), microbarographic measurements were conducted on the Northern Adriatic as a part of research on the Bora. In this paper the measured pressure field around the Dinaric Alps is used to compute the total pressure drag vectors using Archimedes law.The 3-hourly temporal variations of these drag vectors is examined for different synoptic events. During the anticyclonic calm weather period at the end of March and beginning of April there is evidence of a divrnal drag variation. Regardless of magnitude, the pressure drag vectors seem to be aligned almost perpendicular to the main mountain ridge. During synoptic scale flow developments the drag direction change usually appears steady and slow (1–2 days). However during an exceptionally strong frontal passage (8/9 April) this time scale was much shorter (3–6 hours). The maximae of the pressure drag during SOP are always connected with Bora periods and the magnitudes of the drag values indicate that during these events there is a major sink of atmospheric momentum over the Dinaric Alpine region.With 11 Figures  相似文献   

14.
This study investigates the near-ground free convection conditions (FCCs) based on eddy covariance (EC) measurements at Nam Co station near the Nam Co Lake on the Tibetan Plateau (TP). The spatial and temporal structure of EC measurements at this station is evaluated by using the comprehensive software package TK2 together with a footprint model. The obtained high-quality turbulent flux data are used to study the occurrence of FCCs, which can be detected with the EC system by calculating the stability parameter. Two types of generation of FCCs can be identified. (1) During the wind direction change of a diurnal thermally forced land-lake circulation system in the morning, strongly reduced wind speeds and simultaneously high buoyancy fluxes lead to a period of dominance of buoyancy over shear, and hence, to the occurrence of FCCs. (2) On days with the appearance of clouds, the land-lake circulation is weakened or reversed, dependent on the temperature gradients between the land and the Nam Co Lake. During the period of adaptation of the land-lake breeze to the alternating situation of heating differences, wind speeds decrease and buoyancy again dominates over shear near the ground. These are the situations where FCCs are also detected during the entire day at Nam Co station. The investigation of FCCs regarding the whole measurement period shows that FCCs can be mainly attributed to case (1) during the non-monsoon period, while FCCs are generated by both mechanisms (1 and 2) during the monsoon season. An impact of the FCCs on the near-ground profiles of air temperature and humidity is demonstrated. The FCCs are assumed to play an important role for the land surface-atmosphere exchange processes and the atmospheric boundary layer (ABL) conditions on the TP by providing an effective transport mechanism of near-ground air mass characteristics into upper parts of the ABL.  相似文献   

15.
Annual precipitation,evaporation,and calculated accumulation from reanalysis model outputs have been investigated for the Greenland Ice Sheet (GrIS),based on the common period of 1989-2001.The ERA-40 and ERA-interim reanalysis data showed better agreement with observations than do NCEP-1 and NCEP-2 reanalyses.Further,ERA-interim showed the closest spatial distribution of accumulation to the observation.Concerning temporal variations,ERA-interim showed the best correlation with precipitation observations at five synoptic stations,and the best correlation with in situ measurements of accumulation at nine ice core sites.The mean annual precipitation averaged over the whole GrIS from ERA-interim (363 mm yr 1) and mean annual accumulation (319 mm yr 1) are very close to the observations.The validation of accumulation calculated from reanalysis data against ice-core measurements suggests that further improvements to reanalysis models are needed.  相似文献   

16.
Summary The experimental site of the Department of Meteorology of Freiburg University at the Hartheim pine stand is first described. There, since 1973 long term measurements of net radiation and its components have been carried out. In addition we have been monitoring the different heat fluxes and components of the forest water budget.From May 11th to May 24th 1992 a special international and interdisciplinary observation period was organized in Hartheim (HartX 92). This took place in the frame of the international regional climatic project REKLIP (Regionales Klima Projekt). We then describe the permanent equipment and the special HartX installations. After that we show the climate of the region, in May 1992 and the weather during the HartX period. It was extraordinarily warm and the precipitation was much less than normal. The cloud cover was very small.We report the results of the radiation measurements (net radiation and its components). They are compared to the long standing measurements (1974–1988). Moreover the longstanding data of the components of the water budget (throughfall, canopy drip and stemflow, interception and transpiration) of the period 1978–1985 are dealt with. In addition we report the behaviour of the energy fluxes (soil-stand heat flux, turbulent sensible and latent heat fluxes) of the period 1974–1988. These estimations are compared to the conditions in May 1992 and the conditions during HartX 92.With 8 Figures  相似文献   

17.
Summary ¶Many scientists have suggested that variations in cosmic ray flux may impact cloudiness at regional, hemispheric, or global scales. However, considerable debate surrounds (a) whether high or low clouds are most strongly impacted by cosmic rays, (b) the degree of seasonality in cloud responses to cosmic rays, and (c) the determination of physical processes involved in cosmic ray/cloud interactions. Some scientists find strong correlation coefficients between cloud measurements and cosmic ray flux, while others find no relationship whatsoever; virtually all scientists working on this issue are hampered by the relatively short time period with accurate cloud and cosmic ray flux records. In an attempt to extend the period of record, we assembled surface and radiosonde data for the United States over the period 1957–1996 along with sunspot records which are known to be strongly, but inversely, related to cosmic ray flux. We also assembled cloud cover data and cosmic ray measurements over a reduced time period. We found that periods with low sunspot number (times with high cosmic ray flux) are associated with significantly higher dew point depressions, a higher diurnal temperature range, and less cloud cover. Our results do not support suggestions of increased cloud cover during periods of high cosmic ray flux.Received May 14, 2002; accepted February 17, 2003 Published online May 26, 2003  相似文献   

18.
Three comprehensive acid deposition models were used to simulate the sulfur concentrations over northeast Asia over the period covering entire year of 2002, and discussed the aggregated uncertainties and discrepancies of the three models. The participating models are from the countries participating in the project of Longrange Transboundary Air Pollutants in Northeast Asia (LTP): China, Japan and Korea. The Eulerian Model-3/CMAQ (by China), Regional Air Quality Model (RAQM, by Japan), and Comprehensive Acid Deposition Model (CADM, by Korea) were employed by each country with common emissions data established by the administrative agencies of China, Japan and Korea. The episodic simulation results between 1 to 15, March 2002 are also presented, during which aircraft measurements were carried out over the Yellow sea. The episodic results show both a wide short-term variability in simulations against measurements, and maximum concentration differences of 3～5 times among the three models, requiring that further attention before confidence among the three models can be claimed for short-term simulations. However, the year-long cumulative simulations showed almost the same general features, with lower aggregated uncertainties between the three models, produced by the long term integration over northeast Asia.  相似文献   

19.
Photochemical smog characterized by high concentrations of ozone (O3) is a serious air pollution issue in the North China Plain (NCP) region, especially in summer and autumn. For this study, measurements of O3, nitrogen oxides (NOx), volatile organic compounds (VOCs), carbon monoxide (CO), nitrous acid (HONO), and a number of key physical parameters were taken at a suburban site, Xianghe, in the NCP region during the summer of 2018 in order to better understand the photochemical processes leading to O3 formation and find an optimal way to control O3 pollution. Here, the radical chemistry and O3 photochemical budget based on measurement data from 1-23 July using a chemical box model is investigated. The daytime (0600-1800 LST) average production rate of the primary radicals referred to as ROx (OH + HO2+ RO2) is 3.9 ppbv h-1. HONO photolysis is the largest primary ROx source (41％). Reaction of NO2 + OH is the largest contributor to radical termination (41％), followed by reactions of RO2 + NO2 (26％). The average diurnal maximum O3 production and loss rates are 32.9 ppbv h-1 and 4.3 ppbv h-1, respectively. Sensitivity tests without the HONO constraint lead to decreases in daytime average primary ROx production by 55％ and O3 photochemical production by 42％, highlighting the importance of accurate HONO measurements when quantifying the ROx budget and O3 photochemical production. Considering heterogeneous reactions of trace gases and radicals on aerosols, aerosol uptake of HO2 contributes 11％ to ROx sink, and the daytime average O3 photochemical production decreases by 14％. The O3-NOx-VOCs sensitivity shows that the O3 production at Xianghe during the investigation period is mainly controlled by VOCs.  相似文献   

20.
Surface measurements of aerosol physical properties were made at Anantapur(14.62°N,77.65 °E,331 m a.s.l),a semiarid rural site in India,during August 2008-July 2009.Measurements included the segregated sizes of aerosolsas as well as total mass concentration and size distributions of aerosols measured at low relative humidity(RH<75%) using a Quartz Crystal Microbalance(QCM) in the 25-0.05 μm aerodynamic diameter range.The hourly average total surface aerosol mass concentration in a day varied from 15 to 70 μg m-3,with a mean value of 34.02±9.05μgm-3 for the entire study period.A clear diurnal pattern appeared in coarse,accumulation and nucleation-mode particle concentrations,with two local maxima occurring in early morning and late evening hours.The concentration of coarse-mode particles was high during the summer season,with a maximum concentration of 11.81±0.98μgm-3 in the month of April,whereas accumulationmode concentration was observed to be high in the winter period contributed >68% to the total aerosol mass concentration.Accumulation aerosol mass fraction,A f(=Ma/Mt) was highest during winter(mean value of Af～0.80) and lowest(Af～0.64) during the monsoon season.The regression analysis shows that both R eff and R m are dependent on coarse-mode aerosols.The relationship between the simultaneous measurements of daily mean aerosol optical depth at 500 nm(AOD500) and PM 2.5 mass concentration([PM2.5]) shows that surface-level aerosol mass concentration increases with the increase in columnar aerosol optical depth over the observation period.  相似文献   

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