scholarly journals Parameter sensitivity of a distributed enhanced temperature-index melt model

2013 ◽  
Vol 54 (63) ◽  
pp. 311-321 ◽  
Author(s):  
Martin Heynen ◽  
Francesca Pellicciotti ◽  
Marco Carenzo
Keyword(s):  
Model Uncertainty ◽  
Meteorological Data ◽  
Lapse Rate ◽  
Shortwave Radiation ◽  
Temperature Threshold ◽  
Temperature Index ◽  
Temperature Lapse Rate ◽  
Clear Sky ◽  
The Andes ◽  
Optimal Value

AbstractWe investigate the sensitivity of a distributed enhanced temperature-index (ETI) melt model, in order to understand which parameters have the largest influence on model outputs and thus need to be accurately known. We use melt and meteorological data from two Alpine glaciers and one glacier in the Andes of Chile. Sensitivity analysis is conducted in a systematic way in terms of parameters and the different conditions (day, night, clear-sky, overcast), melt seasons and glaciers examined. The sensitivity of total melt to changes in individual parameters is calculated using a local method around the optimal value of the parameters. We verify that the parameters are optimal at the distributed scale and assess the model uncertainty induced by uncertainty in the parameters using a Monte Carlo technique. Model sensitivity to parameters is consistent across melt seasons, glaciers, different conditions and the daily statistics examined. The parameters to which the model is most sensitive are the shortwave-radiation factor, the temperature lapse rate for extrapolation of air temperature, the albedo parameters, the temperature threshold and the cloud transmittance factor parameters. A parameter uncertainty of 5% results in a model uncertainty of 5.6% of mean melt on Haut Glacier d’Arolla, Switzerland.

A New Upper Air Data System—The Transosonde

1956 ◽  
Vol 37 (7) ◽  
pp. 342-350 ◽  
Author(s):  
Albert D. Anderson ◽  
Henry J. Mastenbrook
Keyword(s):  
Constant Pressure ◽  
Meteorological Data ◽  
Data Gathering ◽  
Field Tests ◽  
Primary Source ◽  
Lapse Rate ◽  
Temperature Lapse Rate ◽  
Pressure Surface ◽  
Acceleration And Deceleration ◽  
Wind Velocities

A new concept of upper-air data collection utilizes instrumented balloons controlled to float along given constant-pressure surfaces in the atmosphere. A system of instrumentation, named the transosonde (trans-oceanic-sonde) has been developed for implementing this concept. Field tests have established the technical and meteorological feasibility of the system. In the course of the tests, transosonde balloons were tracked over distances of thousands of miles using a network of shore-based high-frequency radio-direction-finder stations. Emphasis has been placed upon the trajectory of the balloon as the primary source of meteorological data. Wind velocities and accelerations can be derived directly from constant-pressure surface trajectories, providing valuable synoptic and research data. Balloon trajectories in passing through major troughs and ridges define these features, giving information of importance for synoptic analysis and long-range forecasting. In addition, a sequence of trajectories provides a measure of the acceleration and deceleration of these entities. The transosonde system has additional data-gathering potentials for temperature, lapse rate, wind shear and other parameters. It is concluded that the system can be employed over those regions of the globe where upper-air data are lacking at a cost competitive with present-day systems.

scholarly journals O CLIMA E SUA INFLUÊNCIA NA DISTRIBUIÇÃO DA FLORESTA OMBRÓFILA DENSA NA SERRA DA PRATA, MORRETES, PARANÁ

FLORESTA ◽  
2011 ◽  
Vol 41 (3) ◽  
Author(s):  
Christopher Thomas Blum ◽  
Carlos Vellozo Roderjan ◽  
Franklin Galvão
Keyword(s):  
Relative Humidity ◽  
Meteorological Data ◽  
Lapse Rate ◽  
Mountain Range ◽  
Air Masses ◽  
Temperature Lapse Rate ◽  
Serra Do Mar ◽  
Average Temperature ◽  
Climatic Transition ◽  
Apparent Influence

O estudo teve como objetivo caracterizar aspectos climáticos, com enfoque na temperatura e umidade relativa do ar e sua influência sobre a distribuição da vegetação numa encosta da Serra da Prata, Morretes, Paraná, coberta pelas formações Submontana e Montana da Floresta Ombrófila Densa. Entre julho de 2009 e junho de 2010 foram obtidos dados meteorológicos, aos 400 e 1.000 m s.n.m. As temperaturas médias no período foram 19,0 ºC (400 m) e 16,3 ºC (1.000 m). A taxa de redução térmica com a elevação altitudinal foi 0,44 ºC/100 m. Detectou-se uma região de transição climática em torno dos 700 m de altitude, com o clima Cfb acima e o Cfa abaixo. A isoterma da temperatura média de 13 ºC no mês mais frio, estimada para a região dos 800 m s.n.m., coincide com o limite inferior de ocorrência da formação Montana, denotando a influência das baixas temperaturas na diferenciação da vegetação. As médias de umidade relativa do ar foram elevadas, devido ao constante aporte das massas de ar úmido oriundas do oceano. As médias das amplitudes diárias de temperatura e umidade foram muito semelhantes para as duas altitudes, demonstrando que a variação altitudinal parece não exercer influência sobre suas variações diárias na encosta estudada.Palavras-chave:  Gradiente altitudinal; Serra do Mar; Floresta Atlântica; temperatura; umidade relativa do ar. AbstractClimate and his influence over the Atlantic Dense Rainforest distribution in the Prata Mountain Range, Morretes, Paraná, South Brazil. This study aimed to characterize climatic aspects, focusing air temperature and relative humidity, as well as its influence to vegetation distribution in a slope of Prata Mountain Range, Morretes, Paraná, covered by Submontane and Montane formations of the Atlantic Rainforest. Between July of 2009 and June of 2010 meteorological data was collected, at 400 and 1,000 m a.s.l. The average temperature along this period was 19.0 ºC (400 m) and 16.3 ºC (1,000 m). The temperature lapse rate was 0.44 ºC/100 m. It was detected a climatic transition region at about 700 m a.s.l., with the Cfb type above, and the Cfa type below. The isotherm of the average temperature of 13 ºC in the coldest month, estimated for the region of about 800 m a.s.l., agrees with the inferior limit of the Montane formation, denoting influence of low temperatures in the vegetation distinction. The air relative humidity average was high, because the regular arrival of moist air masses from the ocean. The average of daily amplitude of temperature and relative humidity were very similar for both studied altitudes, denoting not apparent influence of the altitudinal variation to the daily variation of these climatic variables in the slope.Keywords:              Altitudinal gradient; Serra do Mar; Atlantic Ombrophilous Dense Forest; temperature; air relative humidity.

scholarly journals Assessing the transferability and robustness of an enhanced temperature-index glacier-melt model

2009 ◽  
Vol 55 (190) ◽  
pp. 258-274 ◽  
Author(s):  
Marco Carenzo ◽  
Francesca Pellicciotti ◽  
Stefan Rimkus ◽  
Paolo Burlando
Keyword(s):  
Energy Balance ◽  
Meteorological Conditions ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Model Parameters ◽  
Radiation Factor ◽  
Temperature Index ◽  
Clear Sky ◽  
Few Data ◽  
Parameter Values

AbstractWe investigate the transferability of an enhanced temperature-index melt model that was developed and tested on Haut Glacier d’Arolla, Switzerland, in the 2001 season. The model’s empirical parameters (temperature factor, TF, and shortwave radiation factor, SRF) are recalibrated for: (1) other locations on Haut Glacier d’Arolla; (2) subperiods of distinct meteorological conditions; (3) different years on Haut Glacier d’Arolla; and (4) other glaciers in different years. The model parameters are optimized against simulations of an energy-balance model validated against ablation observations. Results are compared with those obtained with the original parameters. The model works very well when applied to other sites, seasons and glaciers, with the exception of overcast conditions. Differences are due to underestimation of high melt rates. The parameter values are associated with the prevailing energy-balance conditions, showing that high SRF are obtained on clear-sky days, whereas higher TF are typical of locations where glacier winds prevail and turbulent fluxes are high. We also provide a range of parameters clearly associated with the site’s location and its meteorological characteristics that could help to assign parameter values to sites where few data are available.

scholarly journals Elevated Mixed Layers and Associated Severe Thunderstorm Environments in South and North America

2017 ◽  
Vol 146 (1) ◽  
pp. 3-28 ◽  
Author(s):  
Bruno Z. Ribeiro ◽  
Lance F. Bosart
Keyword(s):  
North America ◽  
South America ◽  
Convective Available Potential Energy ◽  
Lapse Rate ◽  
Synoptic Scale ◽  
Temperature Lapse Rate ◽  
Low Level ◽  
The Andes ◽  
Synoptic Conditions ◽  
Mixed Layers

Abstract This study presents a climatological and composite analysis of elevated mixed layers (EMLs) in South and North America derived from the NCEP Climate Forecast System Reanalysis. The EMLs are identified based on objective criteria applied to the reanalysis data. Composite analyses of synoptic-scale conditions and severe weather parameters associated with spring EML cases are presented. EMLs are more frequent immediately to the east of the Andes and the Rockies. The North American EMLs form by surface heating over the higher terrain of the Rockies, with peak frequency occurring in spring and summer. EMLs in South America are generated by differential temperature advection due to ageostrophic circulations east of the Andes, as indicated by the temperature lapse rate tendency equation, which relates to the higher frequency of EMLs during the cold season in South America. EMLs over North America are about 100 hPa lower than over South America due to the lower height of the Rockies in comparison to the Andes. The synoptic conditions associated with EMLs in South and North America are characterized by an upper-level trough upstream and low-level moisture flux convergence due to poleward-directed flow, favoring synoptic-scale ascent poleward of the EML location, where the convective inhibition is relatively low. When EMLs occur, higher surface-based convective available potential energy and low-level storm-relative helicity, in association with lower lifting condensation level heights observed in North America, indicate that surface-based supercell storms and tornadoes are more likely to occur on this continent in comparison with South America, corroborating observations.

scholarly journals Effect of the relative humidity on an industrial plume behavior

2013 ◽  
Vol 8 (3) ◽  
pp. 297-305
Keyword(s):  
Relative Humidity ◽  
Meteorological Data ◽  
Source Parameters ◽  
Momentum Equation ◽  
Lapse Rate ◽  
Maximum Height ◽  
Atmospheric Conditions ◽  
Empirical Formulas ◽  
Ratio Distribution ◽  
Temperature Lapse Rate

In order to accurately predict the pollutant concentrations and the plume trajectory in the atmosphere, it is necessary to take into account the effects of interactions between the plume and the surrounding environment. In fact, the atmospheric conditions have a lot of influence on the plume behavior. Earlier models were based on statistical approach. However, this approach presents many shortcomings, in that way they are unable to take directly into account some atmospheric properties such as the moisture of the air. A complete model is the one that solves the entire set of momentum equation completed by energy and species equations. A number of approximate predictive methods for the plume flow in stratified surroundings have been developed in the literature such as Abraham (1965), Schwartz and Tulin (1972), Sneck and Brown (1974), Wright (1984) and Hwang and Chiang (1986). In this work, we use the lagrangian concept based on the so-called projected area entrainment in its latest formulation (Lee and Cheung 1990) to predict the effect of relative humidity on the plume behavior. Input-required data include source parameters such as the gas exhaust conditions (temperature release, exit velocity, mixing ratios), physical dimensions (diameter and height of stack) and meteorological data. In the present work, only idealized meteorological conditions which neglect the vertical variation of the wind speed, the temperature lapse rate and the relative humidity are considered. The output of the model gives an idea on characteristics parameters of the plume such as its trajectory, its temperature and mixing ratio distribution and its length of visibility. The model validation is accomplished through a comparison of the computed plume maximum height with results obtained using empirical formulas (Hanna, 1972). Also, the calculated plume visibility length is confronted to the ADMS results obtained by Carruthers et al. (2000). The effect of relative humidity is then investigated.

scholarly journals Characterizing and correcting the warm bias observed in AMDAR temperature observations

2021 ◽  
Author(s):  
Siebren de Haan ◽  
Paul M. A. de Jong ◽  
Jitze van der Meulen
Keyword(s):  
Meteorological Data ◽  
Weather Prediction ◽  
Atmospheric Temperature ◽  
Lapse Rate ◽  
Warm Bias ◽  
Temperature Lapse Rate ◽  
Additional Information ◽  
Temperature Bias ◽  
Temperature Observations ◽  
Nwp Model

Abstract. Some aircraft temperature observations, retrieved through the Aircraft Meteorological Data Relay (AMDAR), suffer from a significant warm bias when comparing observations with numerical weather prediction (NWP) model. In this manuscript we show that this warm bias of AMDAR temperature can be characterized and consequently reduced substantially. The characterization of this warm bias is based on the methodology of measuring temperature with a moving sensor and can be split into two separate processes. The first process depends on the flight phase of the aircraft and relates to difference of timing, as it appears that the time of measurement of altitude and temperature differ. When an aircraft is ascending or descending this will result in small bias in temperature due to the (on average) presence of an atmospheric temperature lapse rate. The second process is related to internal corrections applied to pressure altitude without feedback to temperature observation measurement. Based on NWP model temperature data combined with additional information on Mach number and true airspeed, we were able to estimate corrections using an 18 months period from January 2017 to July 2018. Next, the corrections were applied on AMDAR observations over the period from September 2018 to mid-December 2019. Comparing these corrected temperatures with (independent) radiosonde temperature observations demonstrates a reduction of the temperature bias from 0.5 K to around zero and reduction of standard deviation of almost 10 %.

scholarly journals Assessing glacier melt contribution to streamflow at Universidad Glacier, central Andes of Chile

2017 ◽  
Vol 21 (7) ◽  
pp. 3249-3266 ◽  
Author(s):  
Claudio Bravo ◽  
Thomas Loriaux ◽  
Andrés Rivera ◽  
Ben W. Brock
Keyword(s):  
River Flow ◽  
Meteorological Data ◽  
Late Summer ◽  
Central Andes ◽  
Lapse Rate ◽  
Balance Model ◽  
Flow Measurements ◽  
Temperature Index ◽  
Glacier Melt ◽  
Monthly Streamflow

Abstract. Glacier melt is an important source of water for high Andean rivers in central Chile, especially in dry years, when it can be an important contributor to flows during late summer and autumn. However, few studies have quantified glacier melt contribution to streamflow in this region. To address this shortcoming, we present an analysis of meteorological conditions and ablation for Universidad Glacier, one of the largest valley glaciers in the central Andes of Chile at the head of the Tinguiririca River, for the 2009–2010 ablation season. We used meteorological measurements from two automatic weather stations installed on the glacier to drive a distributed temperature-index and runoff routing model. The temperature-index model was calibrated at the lower weather station site and showed good agreement with melt estimates from an ablation stake and sonic ranger, and with a physically based energy balance model. Total modelled glacier melt is compared with river flow measurements at three sites located between 0.5 and 50 km downstream. Universidad Glacier shows extremely high melt rates over the ablation season which may exceed 10 m water equivalent in the lower ablation area, representing between 10 and 13 % of the mean monthly streamflow at the outlet of the Tinguiririca River Basin between December 2009 and March 2010. This contribution rises to a monthly maximum of almost 20 % in March 2010, demonstrating the importance of glacier runoff to streamflow, particularly in dry years such as 2009–2010. The temperature-index approach benefits from the availability of on-glacier meteorological data, enabling the calculation of the local hourly variable lapse rate, and is suited to high melt regimes, but would not be easily applicable to glaciers further north in Chile where sublimation is more significant.

scholarly journals Cold firn in the Mont Blanc and Monte Rosa areas, European Alps: spatial distribution and statistical models

2002 ◽  
Vol 35 ◽  
pp. 9-18 ◽  
Author(s):  
Stephan Suter ◽  
Martin Hoelzle
Keyword(s):  
Lapse Rate ◽  
Shortwave Radiation ◽  
Turbulent Heat ◽  
European Alps ◽  
Near Surface ◽  
Temperature Lapse Rate ◽  
Turbulent Heat Exchange ◽  
Summit Region ◽  
Lapse Rates ◽  
Monte Rosa

AbstractNear-surface firn temperatures were measured in 22 steam-drilled boreholes in the summit region of Mont Blanc (France and Italy) at 3800 –4800ma.s.l. in June 1998 and in 31 boreholes in the Monte Rosa area (Italy and Switzerland) at 3900– 4500ma.s.l. in May–July 1999. Borehole temperatures were logged to 22 m depth. the temperatures at 18 m depth ranged between temperate conditions and approximately –15˚C. In a small altitude band, the observed distribution pattern suggests a strong influence of shortwave radiation and turbulent heat exchange (being generally more effective at wind-exposed sites). These two energy fluxes mainly determine the melt-energy input into the snow and firn during summer and, thereby, the measured near-surface temperatures. A statistical analysis of the measured firn temperatures revealed altitude-dependent firn temperature gradients of –1.48 and of –2.36˚C (100m)–1 for the Mont Blanc and Monte Rosa areas, respectively. the high lapse rates, as compared to the air-temperature lapse rate, are the result of englacial latent-heat contribution. the parameters elevation, potential direct solar radiation, slope and accumulation explain 480% of the variation of the mean annual firn temperatures. Aspect-dependent lower boundaries for the cold-firn occurrence in the two areas ranged between 3500 and 4100 ma.s.l.

Evaluation of net shortwave radiation over China with a regional climate model

2020 ◽  
Vol 80 (2) ◽  
pp. 147-163
Author(s):  
X Liu ◽  
Y Kang ◽  
Q Liu ◽  
Z Guo ◽  
Y Chen ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Radiant Energy ◽  
Energy System ◽  
Radiation Budget ◽  
Shortwave Radiation ◽  
Monsoon Region ◽  
Clear Sky ◽  
Sky Conditions

The regional climate model RegCM version 4.6, developed by the European Centre for Medium-Range Weather Forecasts Reanalysis, was used to simulate the radiation budget over China. Clouds and the Earth’s Radiant Energy System (CERES) satellite data were utilized to evaluate the simulation results based on 4 radiative components: net shortwave (NSW) radiation at the surface of the earth and top of the atmosphere (TOA) under all-sky and clear-sky conditions. The performance of the model for low-value areas of NSW was superior to that for high-value areas. NSW at the surface and TOA under all-sky conditions was significantly underestimated; the spatial distribution of the bias was negative in the north and positive in the south, bounded by 25°N for the annual and seasonal averaged difference maps. Compared with the all-sky condition, the simulation effect under clear-sky conditions was significantly better, which indicates that the cloud fraction is the key factor affecting the accuracy of the simulation. In particular, the bias of the TOA NSW under the clear-sky condition was <±10 W m-2 in the eastern areas. The performance of the model was better over the eastern monsoon region in winter and autumn for surface NSW under clear-sky conditions, which may be related to different levels of air pollution during each season. Among the 3 areas, the regional average biases overall were largest (negative) over the Qinghai-Tibet alpine region and smallest over the eastern monsoon region.

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