Meteorological Observation Stations Research Articles

Asian dust event observed in Seoul, Korea, during 29–31 May 2008: Analysis of transport and vertical distribution of dust particles from lidar and surface measurements

In this study, we investigate the transport of dust particles, its vertical distribution, and the associated meteorological conditions during an Asian dust event that was observed in Seoul, Korea on May 29-31, 2008. This study analyzes data from ground-based and space-borne 2-wavelength polarization lidars, particulate mass concentrations, and synoptic weather data. Surface meteorological station observations of dust phenomena, dust transport model, and weather maps consistently show that the dust particles were transported from the source regions (Inner Mongolia, Man-Ju, and Ordos areas) to Korea via the northeastern part of China. Network observations of the PM(10) concentrations in Korea revealed that a majority of the heavy dust particles traveled across South Korea from the northwest to the southeast direction with a horizontal scale of 250-300km and a traveling speed of approximately 40kmh(-1). This extraordinary dust event, in terms of its intensity and timing during the year, occurred due to the blockage of an unusually intensified low-pressure system in the northeastern part of China as well as high-pressure system centered over the Sea of Okhotsk and the Kuril Islands. The low values of the particle depolarization ratio (delta(532)) (<or=0.05) and color ratio (CR) during the pre-dust period indicate the presence of spherical, non-dust, and relatively small particles. The mean delta(532) value was approximately 0.123+/-0.069 between altitudes of ground approximately 2.8km, and 0.161+/-0.049 for near-surface dust layer (ground approximately 1.2km). This value is quite similar to that obtained during the 3-year SNU-Lidar measurements in Seoul (delta(532) approximately 0.136+/-0.027). The value of delta(532) during the 2nd multilayered dust episode ranged between 0.081 and 0.120 for near-surface dust layers, and between 0.076 and 0.114 for elevated dust layers. The CALIPSO measurements of beta(532), delta(532), and CR also revealed the presence of dense dust aerosols along the transport route.

Use of regional climate model simulations as input for hydrological models for the Hindukush-Karakorum-Himalaya region

Abstract. The most important climatological inputs required for the calibration and validation of hydrological models are temperature and precipitation that can be derived from observational records or alternatively from regional climate models (RCMs). In this paper, meteorological station observations and results of the PRECIS (Providing REgional Climate for Impact Studies) RCM driven by the outputs of reanalysis ERA 40 data and HadAM3P general circulation model (GCM) results are used as input in the hydrological model. The objective is to investigate the effect of precipitation and temperature simulated with the PRECIS RCM nested in these two data sets on discharge simulated with the HBV model for three river basins in the Hindukush-Karakorum-Himalaya (HKH) region. Six HBV model experiments are designed: HBV-Met, HBV-ERA and HBV-Had, HBV-MetCRU-corrected, HBV-ERABenchmark and HBV-HadBenchmark where HBV is driven by meteorological stations data, data from PRECIS nested in ERA-40 and HadAM3P, meteorological stations CRU corrected data, ERA-40 reanalysis and HadAM3P GCM data, respectively. Present day PRECIS simulations possess strong capacity to simulate spatial patterns of present day climate characteristics. However, also some quantitative biases exist in the HKH region, where PRECIS RCM simulations underestimate temperature and overestimate precipitation with respect to CRU observations. The calibration and validation results of the HBV model experiments show that the performance of HBV-Met is better than the HBV models driven by other data sources. However, using input data series from sources different from the data used in the model calibration shows that HBV-Had is more efficient than other models and HBV-Met has the least absolute relative error with respect to all other models. The uncertainties are higher in least efficient models (i.e. HBV-MetCRU-corrected and HBV-ERABenchmark) where the model parameters are also unrealistic. In terms of both robustness and uncertainty ranges the HBV models calibrated with PRECIS output performed better than other calibrated models except for HBV-Met which has shown a higher robustness. This suggests that in data sparse regions such as the HKH region data from regional climate models may be used as input in hydrological models for climate scenarios studies.

Linking Inuit knowledge and meteorological station observations to understand changing wind patterns at Clyde River, Nunavut

Connecting indigenous and scientific observations and knowledge has received much attention in the Arctic, not least in the area of climate change. On some levels, this connection can be established relatively easily, linking observations of similar phenomena or of various effects stemming from the same cause. Closer examinations of specific environmental parameters, however, can lead to far more complex and difficult attempts to make those connections. In this paper we examine observations of wind at Clyde River, Nunavut, Canada. For Inuit, many activities are governed by environmental conditions. Wind, in particular, is identified by Inuit as one of the most important environmental variables, playing a key role in driving sea ice, ocean, and weather conditions that can either enable or constrain hunting, travel, or other important activities. Inuit observe wind patterns closely, and through many means, as a result of their close connection to the land and sea. Inuit in many parts of Nunavut are reporting changes in wind patterns in recent years. At Clyde River, a community on the eastern coast of Baffin Island, Inuit have observed that at least three key aspects of wind have changed over the last few decades: wind variability, wind speed, and wind direction. At the same time, wind observations are also available from an operational weather station located at Clyde River. An analysis of this information shows little change in wind parameters since the mid-1970s. Though the station data and Inuit observations correspond in some instances, overall, there is limited agreement. Although the differences in the two perspectives may point to possible biases that may exist from both sources—the weather station data may not be representative of the region, Inuit observations or explanations may be inaccurate, or the instrumental and Inuit observations may not be of the same phenomena—they also raise interesting questions about methods for observing wind and the nature of Arctic winds.

Spatial-temporal characteristics of high-temperature events in summer in eastern China and the associated atmospheric circulation

Based on the data for 193 meteorological observation stations in eastern China from 1955 to 2005,the authors analyzed the spatial and temporal characteristics of summer high-temperature events(daily maximum temperature above 35℃).Empirical orthogonal function(EOF) analysis reveals that there are three main patterns for the high-temperature events.The first EOF pattern is Characterized by a uniform anomaly over the whole east China with a center along the Yangtze River valley.The second is a dipole pattern with two centers in southernmost China and the areas to north,and the third mode shows an out of phase pattern between east and west parts of the area.These patterns are tightly related to the atmospheric circulation.The results show that ENSO,Equatorial Indian Ocean and Western Pacific Warm Pool SST could affect the frequency of summer high temperature by influencing the Western Pacific and East Asia atmospheric circulation.ENSO and Western Pacific Warm Pool have a great impact on the first EOF.And the relationship between the second EOF and Equatorial Indian Ocean SST is a significantly negative correlation.The relations between high temperature and the preceding SST of key regions are studied;there are evident positive correlations between the preceding summer SST of Western Pacific Warm Pool and the first EOF,which is negatively correlated with the preceding winter SST of Equatorial East Pacific.And the second EOF is most impacted by the preceding winter SST of Equatorial Indian Ocean.

Correlation of precipitation to temperature variation in the Huanghe River (Yellow River) basin during 1957–2006

summary Based on the data of 88 meteorological observation stations distributed in nine provinces and autonomous regions in Huanghe River (Yellow River) basin of China, time series of annual precipitation and temperature, the frequency and quantity of extreme precipitation per year were analyzed to assess the correlation of precipitation to temperature increasing variation during a 50-year period from 1957 to 2006. The results showed trends of precipitation were constantly decreasing while temperature was increasing in the last five decades. The correlation coefficient between precipitation and temperature demonstrates a statistically significant rising trend over time (p < 0.01). In the upper reach of the basin, a typical arid zone with vulnerable ecosystem, extreme rain events including rainstorms and drought periods are significantly increasing. Compared with the lower reach in semi-humid zone, the precipitation in the arid zone is more responsive to temperature variation.

Assessing the effect of land use/land cover change on the change of urban heat island intensity

Due to rapid economic development, China has experienced one of the greatest rates of change in land use/land cover during the last two decades. This change is mainly urban expansion and cultivated land reduction in urban growth regions, both of which play an important role in regional climate change. In this paper, the variation of the urban heat island (UHI) caused by urbanization has been evaluated with an analysis of land use change in China. First, meteorological observation stations were grouped by different land cover types (dry land, paddy field, forest, grassland, water field, urban, rural inhabitable area, industrial and mineral land, and waste land) throughout China. These stations were subdivided into urban and non-urban classes. Then, a new method was proposed to determine the UHI intensity from the difference between the observed and the interpolated air temperature of urban type weather stations. The results indicate that the trends of UHI intensity in different land use change regions are spatially correlated with regional land use and its change pattern. During 1991-2000, the estimated UHI intensity has increased by 0.11 degrees C per decade in the spring and has fluctuated in other seasons throughout China resulting from land use change.

Estimating evaporation from a wet grassland

Abstract. Wet grasslands are being restored across the UK and Europe to reinstate their high biodiversity following over 50 years of drainage and conversion to arable agriculture. The water balance of many wet grasslands is dominated by precipitation and evaporation and it is essential to quantify evaporation rates to understand the hydrological functioning of wetlands and the implications for water resources in catchments where wetlands are being restored. This paper considers data from direct measurements of evaporation from the Pevensey Levels wet grassland using the eddy correlation method. Equations are derived to predict actual evaporation using meteorological data on the site or from standard meteorological station observations. It was found that evaporation could be estimated reliably from meteorological variables, such as wind speed, temperature and humidity and by water availability. It was also found that when water availability is high, evaporation is high and may exceed reference evaporation values, raising questions over the deployment of the two-step Penman-Monteith model unless reliable crop coefficients and relative evaporation figures can be determined.

NOAA위성영상 및 기상자료를 이용한 융설 관련 매개변수 추출

Establishment of snowmelt factors is necessary to simulate stream flow using snowmelt models during snowmelt periods. The few observed data related snowmelt was the major cause of difficulty in extracting snowmelt factors such as snow cover area, snow depth and depletion curve. The objective of this study was to extract snowmelt factors using RS, GIS technique and meteorological data. Snow cover maps were derived from NOAA/AVHRR images for the winter seasons from 1997 to 2003. Distributed snow depth was mapped by overlapping between snow cover maps and interpolated snowfall maps from 69 meteorological observation station. Depletion curves of snowmelt area were described from the linear regression equations of each year between the average temperature and snow cover area in Soyanggang-dam and chungju-dam watershed.

Climate change in Mt. Qomolangma region since 1971

Using monthly average, maximum, minimum air temperature and mothly precipitation data from 5 weather stations in Mt. Qomolangma region in China from 1971 to 2004, climatic linear trend, moving average, low-pass filter and accumulated variance analysis methods, the spatial and temporal patterns of the climatic change in this region were analyzed. The main findings can be summarized as follows: (1) There is obvious ascending tendency for the interannual change of air temperature in Mt. Qomolangma region and the ascending tendency of Tingri, the highest station, is the most significant. The rate of increasing air temperature is 0.234 °C/decade in Mt. Qomolangma region, 0.302 °C/decade in Tingri. The air temperature increases more strongly in non-growing season. (2) Compared with China and the global average, the warming of Mt. Qomolangma region occurred early. The linear rates of temperature increase in Mt. Qomolangma region exceed those for China and the global average in the same period. This is attributed to the sensitivity of mountainous regions to climate change. (3) The southern and northern parts of Mt. Qomolangma region are quite different in precipitation changes. Stations in the northern part show increasing trends but are not statistically significant. Nyalam in the southern part shows a decreasing trend and the sudden decreasing of precipitation occurred in the early 1990s. (4) Compared with the previous studies, we find that the warming of Mt. Qomolangma high-elevation region is most significant in China in the same period. The highest automatic meteorological comprehensive observation station in the world set up at the base camp of Mt. Qomolangma with a height of 5032 m a.s.l will play an important role in monitoring the global climate change.

Land use/land cover change effects on temperature trends at U.S. Climate Normals stations

Alterations in land use/land cover (LULC) in areas near meteorological observation stations can influence the measurement of climatological variables such as temperature. Urbanization near climate stations has been the focus of considerable research attention, however conversions between non‐urban LULC classes may also have an impact. In this study, trends of minimum, maximum, and average temperature at 366 U.S. Climate Normals stations are analyzed based on changes in LULC defined by the U.S. Land Cover Trends Project. Results indicate relatively few significant temperature trends before periods of greatest LULC change, and these are generally evenly divided between warming and cooling trends. In contrast, after the period of greatest LULC change was observed, 95% of the stations that exhibited significant trends (minimum, maximum, or mean temperature) displayed warming trends.

東京湾における季節特性を考慮した湾内流動の再現計算

This study describes typical mass transports in spring, summer, autumn and winter in Tokyo Bay by using a non-hydrostatic model, MEL3D. Some typical salinity and water temperature distributions in each season obtained from field observation were used in the numerical computation. Furthermore, spatial distributions of wind over Tokyo Bay evaluated using nine meteorological observation stations were applied in the computation as boundary conditions. To investigate mass transport, neutral particle tracking simulations were carried out by putting particles along near the coastal line by about 4km. As the results, especially in summer, it was demonstrated that the characteristic of the neutral particle transport in Tokyo Bay is strongly affected by the vertical current of circulation around the western coast in the head of Tokyo Bay.

Estimating Hourly Direct and Diffuse Solar Radiation for the Compilation of Solar Radiation Distribution Maps

This paper presents a new method for estimating hourly direct and diffuse solar radiation. The essence of the method is the estimation of two important factors related to solar radiation, atmospheric transmittance and a dimensionless parameter, using empirical and physical equations and data from general meteorological observation stations. An equation for atmospheric transmittance of direct solar radiation and a dimensionless parameter representing diffuse solar radiation are developed. The equation is based on multiple regression analysis and uses three parameters as explanatory variates: calculated hourly extraterrestrial solar radiation on a horizontal plane, observed hourly sunshine duration and hourly precipitation as observed at a local meteorological observatory. The dimensionless parameter for estimating a diffuse solar radiation is then determined by linear least squares using observed hourly solar radiation at a local meteorological observatory. The estimated root mean square error (RMSE) of hourly direct and diffuse solar radiation is about 0.0∼0.2 MJ·m-2·h-1 in each mean period. The RMSE of the ten-day and monthly means of these quantities is about 0.0∼0.2 MJ·m-2·h-1, based on comparisons with AMeDAS station data, located at a distance of 6 km.

Regional characteristics of three kinds of dust storm events in China

The regional characteristics of dust storm events including dust storm, blowing dust and floating dust in China have been studied by using the data from 701 meteorological observation stations during 1954–2000. The results are as follows: in China, there are two main areas (the South Xinjiang Region and the Hexi Region) where dust storm events happen the most frequently. The spatial distributions of the three types of dust storm events are different. Dust storms mainly occur in the arid and semiarid areas in Northern China. Blowing dust and floating dust not only occur in those areas, but also in neighboring areas. Compared with dust storm and blowing dust, the floating dust very seldom occurs in high-latitude areas. The frequencies of dust storm events decreased generally during 1954–2000. However, they have gradually increased since 1998. The interannual variations of dust storm events showed some characters including two cycles of 3–4 and 11–12 years. The annual changes of the dust storm events were characterized by a strong unimodal distribution with spring maximum. The daily variation of the dust storm occurrence was remarkable, most of dust storms happened in the afternoon, especially between 18:01–21:00 LST. The areas of dust storms could be divided into seven sub-regions. The most frequent areas of dust storms and floating dust were in the South Xinjiang Region, but that of blowing dust was in the Hexi Region. Their maximum interannual variance also happened in both areas. Dust storm events generally occurred most frequently in April in most parts of China, but it happened a little earlier in the Qinghai-Xizang Region and a little later in the Xinjiang Region. The months in which dust storm events occurred more frequently were relatively concentrated in the Northeastern Region and Hetao Region, but were relatively dispersed in the Xinjiang Region.

Climate Effects of the Deep Continental Stratus Clouds Generated by the Tibetan Plateau

Evidence is presented to show that the maximum annual mean cloud optical depth between 60°S and 60°N is located on the lee side of the Tibetan Plateau. This largest cloud optical depth is produced by persistent deep stratus clouds (primarily the nimbostratus and altostratus) during winter and spring. These deep stratus clouds are generated and maintained by the frictional and blocking effects of the Tibetan Plateau. The plateau slows down the overflow, inducing downstream midlevel divergence; meanwhile it forces the low-level flows to converge downstream, generating sustained large-scale lifting and stable stratification that maintain the thick stratus clouds. These stratus clouds produce extremely strong cloud radiative forcing at the top of the atmosphere, which fundamentally influences the local energy balance and climate change. Analysis of the long-term meteorological station observations reveals that the monthly mean anomalous cloudiness and surface temperature vary in tandem. In addition, the surface warming leads to destabilization and desaturation in the boundary layer. This evidence suggests a positive feedback between the continental stratus clouds and surface temperature through changing lower-tropospheric relative humidity and stratification. It is shown that the positive feedback mechanism is more robust during the period of the surface cooling than during the surface warming. It is suggested that the positive climate feedback of the continental stratus cloud may be instrumental in understanding the long-term climatic trend and variations over East Asia.

Trend of Salt Lake Changes in the Background of Global Warming and Tactics for Adaptation to the Changes

Abstract Salt lakes are a mirror of climatic changes and provide holographic records of environmental changes of lakes. According to a study of geological hazards in typical salt lake areas in China and other regions, the authors explain how geological hazards in salt lake areas are caused by natural agents and how humans can seek benefits, avoid hazards and reduce losses on the premise that they have monitored and mastered the trend of salt lake changes in advance and even can store flood and recharge water in lakes and extract saline resources. The climate in western China is probably turning from warm‐dry to warm‐moist. The authors analyze the change trend of salt lakes sensu lato (with salinity≥0.3 wt% (NaCl)eq) and salt lakes sensu stricto (with salinity ≥3.5 wt% (NaCl)eq) in China in such climatic conditions and distinguish three types of salt lake areas (i.e. lake water rising type, lake water falling type and lake water rising and unstable type) according to the characteristics of lake water rising and shrinking. In order to conform to the climatic and lake changes in China's salt lake areas, the authors propose to add and improve hydrological and meteorological observation stations and integrate observations with remote sensing monitoring in important salt lake areas and set up multidisciplinary and interdepartmental basic projects to monitor and study recent climatic and environmental changes in salt lake areas of western China. Moreover, it is necessary to build additional flood‐control and drought‐preventing water conservancy facilities in key salt lake areas and work out measures for ecological protection in salt lake areas. Full consideration should be given to the influence of flooding when building saltfields and implementing capital projects.

Tracing Technique of Atmospheric Waves with Wavelet Transformation

The few observed data related snowmelt was the major cause of difficulty in extracting snowmelt factors such as snow cover area, snow depth and depletion curve. Remote sensing technology is very effective to observe a wide area. Although many researchers have used remote sensing for snow observation, there were a few discussions on the characteristics of spatial and temporal variation. Snow cover maps were derived from NOAA AVHRR images for the winter seasons from 1997 to 2006. Distributed snow depth was mapped by overlapping between snow cover maps and interpolated snowfall maps from 69 meteorological observation stations. Model parameters (Snow Cover Area: SCA, snow depth, Snow cover Depletion Curve: SDC) building for 5 major watersheds in South Korea. Especially SDC is important parameter of snowmelt model.

The bivariate lognormal distribution for describing joint statistical properties of a multivariate storm event

AbstractThe bivariate lognormal distribution is proposed as a model for the joint distribution of storm peak (maximum rainfall intensity) and storm amount. Using the marginal distributions, the joint distribution, the conditional distributions, and the associated return periods are derived. The model is found appropriate for representing multiple episodic storm events at the Motoyama meteorological observation station in Japan. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Inference of surface and air temperature, atmospheric precipitable water and vapor pressure deficit using Advanced Very High-Resolution Radiometer satellite observations: comparison with field observations

Surface temperature (Ts), air temperature (Ta), atmospheric precipitable water (U), and vapor pressure deficit (D) have been derived from algorithms that use satellite observations of visible, near infrared and thermal infrared radiation in order to obtain higher spatial resolution data than is possible from meteorological station observations. The inferences of these four variables are compared with field instrument observations for sites with contrasted climates and vegetation including boreal forest (BOREAS), tropical bush savanna (HAPEX-Sahel), tall-grass prairie (FIFE) and a region with mountain, prairie and intensive agriculture (Red- and Arkansas-river catchments). The results showed that Ts could be retrieved with RMS errors of 3.5°C for a range of 48°C; Ta with 3.9°C over a range of 36°C; U with 0.6 cm over a range of 3.6 cm; and D with 10.9 mb over a range of 58 mb. Although the results had low absolute accuracies, the field data themselves are not without error—not least because, although the inferences were for a >1 km2 area made instantaneously, they were compared with point field values generally not measured at exactly the same times in the day. Maps of retrieved variables had good relative accuracy and possibly better absolute accuracy than the comparisons with point measurements suggest.

Inversion Characteristics in a Valley

The article shows some aspects of the temperature climate in a valley and its surroundings at Máze on Finnmarksvidda, where three meteorological observation stations have been in operation since the autumn of 1981. The stations are situated at the bottom, on the side and at the top of the valley.Temperature inversions are most frequent in the winter and, during the period of observation, especially frequent in December. As expected, inversions are uncommon in the summer. The frequency of inversion shows no variation during the day in the months November, December and January. The greatest daily variation takes place in the season February-May.Inversions are more frequent in cold winters than in mild winters. But in the interval below -15°C there is no correlation between the monthly mean temperature and the frequency of the valley inversion. In extremely cold weather the inversion near the valley floor is often weak and may even be missing.Temperature inversions in the valley very decisively affect the temperature data so that the mean temperature increases with elevation in the season from November to March.

The Penetration of Rainfall through Hardwood and Softwood Forest Canopy

In connection with a study of forest-fire hazard being conducted at the Petawawa Forest Experiment Station of the Dominion Forest Service, Department of the Interior, Canada, at Chalk River, Ontario, an investigation was made, during the 1933 fire season, of the proportion of the rainfall recorded in the open which reaches the forest floor under stands with nearly full canopy. Measurements of rainfall in the open were made at the meteorological observation station operated at the Petawawa Forest Experiment Station. A non-recording gauge of conventional pattern was used for comparison with similar gauges in the forest. The rims of all gauges were about six inches above the ground. Readings were made twice daily in the open, and once a day in the forest. A softwood stand typical of the region was selected about one mile east of the point where the meteorological equipment was located. This was of mixed white and red pine (P. strobus, P. resinosa), 40 years old, with a crown density of 96 per cent as determined by the Clement's photometer. Within an area of 100 square yards in this forest, five rain gauges were disposed as follows: