scholarly journals Evaluation of a Numerical Weather Forecast Model Using Boundary Layer Cloud-Top Temperature Retrieved from AVHRR

2004 ◽  
Vol 132 (4) ◽  
pp. 915-928 ◽  
Author(s):  
A. Mathieu ◽  
A. Lahellec ◽  
A. Weill
Keyword(s):  
Boundary Layer ◽  
Weather Forecast ◽  
Forecast Model ◽  
Numerical Weather ◽  
Weather Forecast Model ◽  
Boundary Layer Cloud ◽  
Numerical Weather Forecast ◽  
Cloud Top Temperature ◽  
Layer Cloud

scholarly journals Sensitivity of a long-range numerical weather forecast model to small changes of model parameters

2011 ◽  
Vol 6 (1) ◽  
pp. 13-18 ◽  
Author(s):  
M. B. Gavrilov ◽  
G. R. Jovanović ◽  
Z. Janjić
Keyword(s):  
Initial Conditions ◽  
Weather Forecast ◽  
Forecast Model ◽  
Model Parameters ◽  
Weather Forecasts ◽  
Numerical Weather ◽  
First Case ◽  
Weather Forecast Model ◽  
Model Setup ◽  
Numerical Weather Forecast

Abstract. Sensitivity of extended-range numerical weather forecasts to small changes of model parameters is studied for two cases. In the first case the Earth radius was perturbed. In the other case changes of the gravity were introduced. The results for the 500 hPa geopotential fields are presented on hemispheric maps and intercompared visually and using RMS differences of the perturbed and reference forecasts. During about the first 10 days of integration the results indicate modest sensitivity of the forecasts to the parameter variation. After this period the forecasts diverge rapidly and start to differ significantly. Repeated integrations on the same computer using the same model setup and the same initial conditions yield identical results.

scholarly journals Continuous monitoring of the boundary-layer top with lidar

2008 ◽  
Vol 8 (3) ◽  
pp. 10749-10790 ◽  
Author(s):  
H. Baars ◽  
A. Ansmann ◽  
R. Engelmann ◽  
D. Althausen
Keyword(s):  
Boundary Layer ◽  
Weather Forecast ◽  
Forecast Model ◽  
Raman Lidar ◽  
Data Set ◽  
Weather Forecast Model ◽  
One Year ◽  
The One ◽  
Lidar Observations

Abstract. Continuous lidar observations of the top height of the boundary layer (BL top) have been performed at Leipzig (51.3° N, 12.4° E), Germany, since August 2005. The results of measurements taken with a compact, automated Raman lidar over a one-year period (February 2006 to January 2007) are presented. Four different methods for the determination of the BL top are discussed. The most promising technique, the wavelet covariance algorithm, is improved by implementing some modifications so that an automated, robust retrieval of BL depths from lidar data is possible. Three case studies of simultaneous observations with the Raman lidar, a vertical-wind Doppler lidar, and accompanying radiosonde profiling of temperature and humidity are discussed to demonstrate the potential and the limits of the four lidar techniques at different aerosol and meteorological conditions. The lidar-derived BL top heights are compared with respective values derived from predictions of the regional weather forecast model COSMO of the German Meteorological Service. The comparison shows a general underestimation of the BL top by about 20% by the model. The statistical analysis of the one-year data set reveals that the seasonal mean of the daytime maximum BL top is 1400 m in spring, 1800 m in summer, 1200 m in autumn, and 800 m in winter at the continental, central European site. BL top typically increases by 100–300 m per hour in the morning of convective days.

scholarly journals Continuous monitoring of the boundary-layer top with lidar

2008 ◽  
Vol 8 (23) ◽  
pp. 7281-7296 ◽  
Author(s):  
H. Baars ◽  
A. Ansmann ◽  
R. Engelmann ◽  
D. Althausen
Keyword(s):  
Boundary Layer ◽  
Weather Forecast ◽  
Forecast Model ◽  
Raman Lidar ◽  
Data Set ◽  
Weather Forecast Model ◽  
One Year ◽  
The One ◽  
Lidar Observations

Abstract. Continuous lidar observations of the top height of the boundary layer (BL top) have been performed at Leipzig (51.3° N, 12.4° E), Germany, since August 2005. The results of measurements taken with a compact, automated Raman lidar over a one–year period (February 2006 to January 2007) are presented. Main goals of the study are (a) to demonstrate that BL top monitoring with lidar throughout the year is possible, (b) to present the required data analysis method that permits an automated, robust retrieval of BL top at all weather situations, and (c) to use this opportunity to compare the lidar-derived BL top data with respective BL tops hourly predicted by the regional weather forecast model COSMO. Four different lidar methods for the determination of the BL top are discussed. The wavelet covariance algorithm is modified so that an automated retrieval of BL depths from lidar data is possible. Three case studies of simultaneous observations with the Raman lidar, a vertical-wind Doppler lidar, and accompanying radiosonde profiling of temperature and humidity are presented to compare the potential and the limits of the four lidar techniques. The statistical analysis of the one-year data set reveals that the seasonal mean of the daytime (about 08:00–20:00 Local Time, LT) maximum BL top is 1400 m in spring, 1800 m in summer, 1200 m in autumn, and 800 m in winter at the continental, central European site. BL top typically increases by 100–300 m per hour in the morning of convective days. The comparison between the lidar-derived BL top heights and the predictions of COSMO yields a general underestimation of the BL top by about 20% by the model.

Boundary Layer, Cloud, and Drizzle Variability in the Southeast Pacific Stratocumulus Regime

2008 ◽  
Vol 21 (23) ◽  
pp. 6191-6214 ◽  
Author(s):  
Efthymios Serpetzoglou ◽  
Bruce A. Albrecht ◽  
Pavlos Kollias ◽  
Christopher W. Fairall
Keyword(s):  
Boundary Layer ◽  
Layer Structure ◽  
Substantial Impact ◽  
Factors Affecting ◽  
Synoptic Conditions ◽  
Southeast Pacific ◽  
Boundary Layer Cloud ◽  
Similar Area ◽  
Earth’S Climate ◽  
Layer Cloud

Abstract The southeast Pacific stratocumulus regime is an important component of the earth’s climate system because of its substantial impact on albedo. Observational studies of this cloud regime have been limited, but during the past 5 yr, a series of cruises with research vessels equipped with in situ and remote sensing systems have provided unprecedented observations of boundary layer cloud and drizzle structures. These cruises started with the East Pacific Investigation of Climate (EPIC) 2001 field experiment, followed by cruises in a similar area in 2003 and 2004 [Pan-American Climate Studies (PACS) Stratus cruises]. The sampling from these three cruises provides a sufficient dataset to study the variability occurring over this region. This study compares observations from the 2004 cruise with those obtained during the previous two cruises. Observations from the ship provide information about boundary layer structure, fractional cloudiness, cloud depth, and drizzle characteristics. This study indicates more strongly decoupled boundary layers during the 2004 cruise than the well-mixed conditions that dominated the cloud and boundary layer structures during the EPIC cruise, and the highly variable conditions—sharp transitions from a solid stratus deck to broken-cloud and clear-sky periods—encountered during PACS Stratus 2003. Diurnal forcing and synoptic conditions are considered to be factors affecting these variations. A statistical evaluation of the macrophysical boundary layer, cloud, and drizzle properties is performed using the 5–6-day periods for which the research vessels remained stationed at the location of 20°S, 85°W during each cruise.

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