An Assessment of Numerical Weather Prediction–Derived Low-Cloud-Base Height Forecasts

Abstract As demand for flight operations in Antarctica grows, accurate weather forecasting of cloud properties such as extent, cloud base, and cloud-top altitude becomes essential. The primary aims of this work are to ascertain relationships between numerical weather prediction (NWP) model output variables and surface-observed cloud properties and to develop low-cloud-base (<2000 m) height prediction algorithms for use across Antarctica to assist in low-cloud forecasting for aircraft operations. NWP output and radiosonde data are assessed against surface observations, and the relationship between the relative humidity RH profile and the height of the observed low-cloud base is investigated. The ability of NWP-derived RH and ice–water cloud optical depth profiles to represent the observed low-cloud conditions around each of the three Australian stations in East Antarctica is assessed. NWP-derived RH is drier than that reported by radiosonde from ground level up to ~2000 m. This trend reverses in the higher troposphere, and the largest positive difference is observed at ~10 000 m. A consequence is very low RH thresholds are needed for low-cloud-base height prediction using NWP RH profiles. RH and optical depth–based threshold techniques all show skill in reproducing the observed cloud-base height at all Australian Antarctic stations, but the radiosonde-derived RH technique is superior in all cases. This comparison of three low-cloud-base height retrieval techniques provides the first documented assessment of the relative efficacy of each technique in Antarctica.

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Prediction of Regional Global Horizontal Irradiance Combining Ground-Based Cloud Observation and Numerical Weather Prediction

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1073-1076.388 ◽

2014 ◽

Vol 1073-1076 ◽

pp. 388-394 ◽

Cited By ~ 4

Author(s):

Fang Cui ◽

Rong Rong Ju ◽

Yu Yu Ding ◽

Huang Ding ◽

Xu Cheng

Keyword(s):

Numerical Weather Prediction ◽

Weather Prediction ◽

Test Site ◽

Numerical Weather Prediction Model ◽

Cloud Base ◽

Short Term ◽

Numerical Weather ◽

Set Up ◽

Prediction Approach ◽

Cloud Base Height

This paper presents a novel very-short term GHI prediction approach which combines ground-based sky images derived cloud map forecast and cloud base height estimated using numerical weather prediction output. To achieve accurate cloud map forecast, a transformation of original sky images is proceeded to eliminate spherical and coordinate distortion. A WRF based numerical weather prediction model is set up to forecast the local meteorological parameters and estimate cloud base heights information. The cloud base height estimation is adopted to derive real locations and sizes of clouds, and eventually obtain very-short term forecast of the local global horizontal irradiance. The validation of the proposed method is carried out by comparing predicted and measured irradiance of a test site. The results show that the method has high prediction accuracy, and has ability to predict the radiation fluctuation caused by the cloud sheltering process.

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Characterization of downwelling radiance measured from a ground-based microwave radiometer using numerical weather prediction model data

Atmospheric Measurement Techniques ◽

10.5194/amt-9-281-2016 ◽

2016 ◽

Vol 9 (1) ◽

pp. 281-293 ◽

Cited By ~ 3

Author(s):

M.-H. Ahn ◽

H. Y. Won ◽

D. Han ◽

Y.-H. Kim ◽

J.-C. Ha

Keyword(s):

Prediction Model ◽

Numerical Weather Prediction ◽

Reference Data ◽

Weather Prediction ◽

Numerical Weather Prediction Model ◽

Radiosonde Data ◽

Absolute Calibration ◽

Observation Data ◽

Numerical Weather ◽

Better Than

Abstract. The ground-based microwave sounding radiometers installed at nine weather stations of Korea Meteorological Administration alongside with the wind profilers have been operating for more than 4 years. Here we apply a process to assess the characteristics of the observation data by comparing the measured brightness temperature (Tb) with reference data. For the current study, the reference data are prepared by the radiative transfer simulation with the temperature and humidity profiles from the numerical weather prediction model instead of the conventional radiosonde data. Based on the 3 years of data, from 2010 to 2012, we were able to characterize the effects of the absolute calibration on the quality of the measured Tb. We also showed that when clouds are present the comparison with the model has a high variability due to presence of cloud liquid water therefore making cloudy data not suitable for assessment of the radiometer's performance. Finally we showed that differences between modeled and measured brightness temperatures are unlikely due to a shift in the selection of the center frequency but more likely due to spectroscopy issues in the wings of the 60 GHz absorption band. With a proper consideration of data affected by these two effects, it is shown that there is an excellent agreement between the measured and simulated Tb. The regression coefficients are better than 0.97 along with the bias value of better than 1.0 K except for the 52.28 GHz channel which shows a rather large bias and variability of −2.6 and 1.8 K, respectively.

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Humidity sensor failure: a problem that should not be neglected by the numerical weather prediction community

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-7-6625-2014 ◽

2014 ◽

Vol 7 (7) ◽

pp. 6625-6649

Author(s):

Y. Liu ◽

N. Tang

Keyword(s):

Relative Humidity ◽

Numerical Weather Prediction ◽

Humidity Sensor ◽

Weather Prediction ◽

Radiosonde Data ◽

Control Procedure ◽

Sensor Failure ◽

Satellite Mission ◽

Numerical Weather ◽

Weather And Climate

Abstract. In this paper, a new issue that very low relative humidity observations exist in a deeper atmosphere layer in the low- and mid-troposphere is studied on the basis of the global radiosonde observations from December 2008 to November 2009, and the humidity retrieval productions from Formosa Satellite mission-3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC, referred to as COSMIC hereafter) in the same period. Results show that these extremely dry relative humidity observations are considerable universal in the worldwide operational radiosonde data. Globally, the annual average occurrence probability of the extremely dry relative humidity is of 4.2%. These measurements usually occur between 20° and 40° latitudes in both Northern and Southern Hemispheres, and in the height from 700 to 450 hPa in the low- and mid-troposphere. Winter and spring are the favoured seasons for these extremely dry humidity observations, with the maximum ratio of 9.53% in the Northern Hemisphere and 16.82% in the Southern Hemisphere. The phenomenon is mainly related to the performance of the radiosonde humidity sensor and the cloud types traversed by the radiosonde balloon. These extremely low relative humidity observations are erroneous, which cannot represent the real atmospheric status, and are likely caused by the failure of humidity sensor. However, these observations have been archived as the formal data. It will affect the reliability of numerical weather prediction, the analysis of weather and climate, if the quality control procedure is not applied.

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Impact of Radiosonde Balloon Drift on Numerical Weather Prediction and Verification

Weather and Forecasting ◽

10.1175/waf-d-12-00114.1 ◽

2013 ◽

Vol 28 (3) ◽

pp. 772-782 ◽

Cited By ~ 19

Author(s):

Stéphane Laroche ◽

Réal Sarrazin

Keyword(s):

Data Assimilation ◽

Numerical Weather Prediction ◽

Weather Prediction ◽

Radiosonde Data ◽

Horizontal Wind ◽

Numerical Weather ◽

Ascent Time ◽

Verification Systems ◽

The Impact ◽

Range Forecasts

Abstract Radiosonde observations employed in real-time numerical weather prediction (NWP) applications are disseminated through the Global Telecommunication System (GTS) using alphanumeric codes. These codes do not include information about the position and elapsed ascent time of the balloon. Consequently, the horizontal balloon drift has generally been either ignored or estimated in data assimilation systems for NWP. With the increasing resolution of atmospheric models, it is now important to consider the positions and times of radiosonde data in both data assimilation and forecast verification systems. This information is now available in the Binary Universal Form for the Representation of Meteorological Data (BUFR) code for radiosonde data. This latter code will progressively replace the alphanumeric codes for all radiosonde data transmitted on the GTS. As a result, a strategy should be adopted by NWP centers to deal with the various codes for radiosonde data during this transition. In this work, a method for estimating the balloon drift position from reported horizontal wind components and a representative elapsed ascent time profile are developed and tested. This allows for estimating the missing positions and times information of radiosonde data in alphanumeric reports, and then for processing them like those available in BUFR code. The impact of neglecting the balloon position in data assimilation and verification systems is shown to be significant in short-range forecasts in the upper troposphere and stratosphere, especially for the zonal wind field in the Northern Hemisphere winter season. Medium-range forecasts are also improved overall when the horizontal position of radiosonde data is retrieved.

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Assessment of the Impact of Observations on Analyses Derived from Observing System Experiments

Monthly Weather Review ◽

10.1175/mwr-d-10-05010.1 ◽

2012 ◽

Vol 140 (1) ◽

pp. 245-257 ◽

Cited By ~ 10

Author(s):

Cristina Lupu ◽

Pierre Gauthier ◽

Stéphane Laroche

Keyword(s):

North America ◽

Numerical Weather Prediction ◽

Weather Prediction ◽

Radiosonde Data ◽

Prediction System ◽

Numerical Weather ◽

Amount Of Information ◽

The North ◽

The Impact ◽

Assimilation System

Abstract Observing system experiments (OSEs) are commonly used to quantify the impact of different observation types on forecasts produced by a specific numerical weather prediction system. Recently, methods based on degree of freedom for signal (DFS) have been implemented to diagnose the impact of observations on the analyses. In this paper, the DFS is used as a diagnostic to estimate the amount of information brought by subsets of observations in the context of OSEs. This study is interested in the evaluation of the North American observing networks applied to OSEs performed at the Meteorological Service of Canada for the period of January and February 2007. The relative values of the main observing networks over North America derived from DFS calculations are compared with those from OSEs in which aircraft or radiosonde data have been removed. The results show that removing some observation types from the assimilation system influences the effective weight of the remaining assimilated observations, which may have an increased impact to compensate for the removal of other observations. The response of the remaining observations when a given set of observations is denied is illustrated comparing DFS calculations with the observations’ impact estimated from OSEs.

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The Accuracy of Solar Irradiance Calculations Used in Mesoscale Numerical Weather Prediction

Monthly Weather Review ◽

10.1175/mwr2886.1 ◽

2005 ◽

Vol 133 (4) ◽

pp. 783-792 ◽

Cited By ~ 57

Author(s):

Robert J. Zamora ◽

Ellsworth G. Dutton ◽

Michael Trainer ◽

Stuart A. McKeen ◽

James M. Wilczak ◽

...

Keyword(s):

Air Quality ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Numerical Weather Prediction ◽

Solar Irradiance ◽

Weather Prediction ◽

The United States ◽

Model Errors ◽

Numerical Weather ◽

Mesoscale Numerical Weather Prediction

In this paper, solar irradiance forecasts made by mesoscale numerical weather prediction models are compared with observations taken during three air-quality experiments in various parts of the United States. The authors evaluated the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) and the National Centers for Environmental Prediction (NCEP) Eta Model. The observations were taken during the 2000 Texas Air Quality Experiment (TexAQS), the 2000 Central California Ozone Study (CCOS), and the New England Air Quality Study (NEAQS) 2002. The accuracy of the model forecast irradiances show a strong dependence on the aerosol optical depth. Model errors on the order of 100 W m−2 are possible when the aerosol optical depth exceeds 0.1. For smaller aerosol optical depths, the climatological attenuation used in the models yields solar irradiance estimates that are in good agreement with the observations.

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Effects of aerosols on clear-sky solar radiation in the ALADIN-HIRLAM NWP system

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-5933-2016 ◽

2016 ◽

Vol 16 (9) ◽

pp. 5933-5948 ◽

Cited By ~ 10

Author(s):

Emily Gleeson ◽

Velle Toll ◽

Kristian Pagh Nielsen ◽

Laura Rontu ◽

Ján Mašek

Keyword(s):

Optical Properties ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Numerical Weather Prediction ◽

Weather Prediction ◽

Radiative Effect ◽

Aerosol Optical Properties ◽

Numerical Weather ◽

Clear Sky ◽

Radiation Scheme

Abstract. The direct shortwave radiative effect of aerosols under clear-sky conditions in the Aire Limitee Adaptation dynamique Developpement InterNational – High Resolution Limited Area Model (ALADIN-HIRLAM) numerical weather prediction system was investigated using three shortwave radiation schemes in diagnostic single-column experiments: the Integrated Forecast System (IFS), acraneb2 and the hlradia radiation schemes. The multi-band IFS scheme was formerly used operationally by the European Centre for Medium Range Weather Forecasts (ECMWF) whereas hlradia and acraneb2 are broadband schemes. The former is a new version of the HIRLAM radiation scheme while acraneb2 is the radiation scheme in the ALARO-1 physics package. The aim was to evaluate the strengths and weaknesses of the numerical weather prediction (NWP) system regarding aerosols and to prepare it for use of real-time aerosol information. The experiments were run with particular focus on the August 2010 Russian wildfire case. Each of the three radiation schemes accurately (within ±4 % at midday) simulates the direct shortwave aerosol effect when observed aerosol optical properties are used. When the aerosols were excluded from the simulations, errors of more than +15 % in global shortwave irradiance were found at midday, with the error reduced to +10 % when standard climatological aerosols were used. An error of −11 % was seen at midday if only observed aerosol optical depths at 550 nm, and not observation-based spectral dependence of aerosol optical depth, single scattering albedos and asymmetry factors, were included in the simulations. This demonstrates the importance of using the correct aerosol optical properties. The dependency of the direct radiative effect of aerosols on relative humidity was tested and shown to be within ±6 % in this case. By modifying the assumptions about the shape of the IFS climatological vertical aerosol profile, the inherent uncertainties associated with assuming fixed vertical profiles were investigated. The shortwave heating rates in the boundary layer changed by up to a factor of 2 in response to the aerosol vertical distribution without changing the total aerosol optical depth. Finally, we tested the radiative transfer approximations used in the three radiation schemes for typical aerosol optical properties compared to the accurate DISORT model. These approximations are found to be accurate to within ±13 % even for large aerosol loads.

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