scholarly journals Impacts of Assimilation of Satellite and Rawinsonde Observations on Southern Hemisphere Baroclinic Wave Activity in the NCEP–NCAR Reanalysis

2008 ◽  
Vol 21 (13) ◽  
pp. 3290-3309 ◽  
Author(s):  
Yanjuan Guo ◽  
Edmund K. M. Chang
Keyword(s):  
Southern Hemisphere ◽  
Satellite Data ◽  
Wave Activity ◽  
Baroclinic Wave ◽  
Weather Forecasts ◽  
Medium Range ◽  
The Difference ◽  
The Impact ◽  
The Waves ◽  
Rawinsonde Data

Abstract In this study, the impacts of the assimilation of satellite and rawinsonde observations on Southern Hemisphere (SH) baroclinic wave activity in the NCEP–NCAR reanalysis are examined by comparing analyses made with and without the assimilation of satellite data (SAT and NOSAT, respectively) for the year 1979, as well as by comparing analyses to the corresponding first guesses from 1958 to 1999. Comparing the eddy kinetic energy (EKE) computed based on the SAT and NOSAT analyses, it is found that the assimilation of satellite data generally decreases the EKE in the SH, which is the opposite of the findings for the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) in previous studies. The decrease of EKE by satellite data in the NCEP–NCAR reanalysis can be traced back to a low bias in retrieved satellite temperature (SATEMP) variance. The eddy available potential energy (EPE) is decreased even more than the EKE with the assimilation of SATEMP, making the waves more barotropic in the SAT analysis. The EKE analysis increment, that is, the difference between the EKE based on analysis and first guess, is a good quantity to indicate the impacts of all observations assimilated. In the NOSAT analysis, positive EKE analysis increments are found around the SH rawinsonde stations, indicating that the assimilation of rawinsonde data increases EKE significantly from the first guess. This also suggests that the NCEP–NCAR first guess is probably biased low. Positive analysis increments around the rawinsonde stations become even larger in the SAT analysis compared with the NOSAT, suggesting that with the assimilation of low-biased SATEMP data, the EKE in the analysis (the initial condition for next time) and hence the first guess is reduced, therefore the rawinsonde observations have to further increase the EKE from the first guess. The patterns of EKE increment from the presatellite (1958–77) and satellite (1979–99) eras show high degrees of similarities to the NOSAT and SAT reanalysis patterns, respectively, lending further support to these findings. The impact of the assimilation of satellite data on the trend of SH baroclinic wave activity is discussed. Positive trends in the SH EKE are found in both the NCEP–NCAR and ERA-40 reanalyses during 1958–99. After taking the impacts of satellite data into account, the EKE trend in the NCEP–NCAR reanalysis gets stronger, while that in the ERA-40 is largely weakened, which adds complications to assessing the real trend in SH baroclinic wave activity. Comparisons among the variances based on the two reanalyses, NCEP–NCAR first guess, SATEMP, and rawinsonde observations are presented to substantiate some of the findings discussed above, such as the low bias in energy in NCEP–NCAR first guess and SATEMP variance.

Impact of planetary waves on infrasound propagation uncertainties

2021 ◽  
Author(s):  
Elisabeth Blanc ◽  
Patrick Hupe ◽  
Bernd Kaifler ◽  
Natalie Kaifler ◽  
Alexis Le Pichon ◽  
...  
Keyword(s):  
Wave Activity ◽  
Atmospheric Dynamics ◽  
Planetary Waves ◽  
Data Sets ◽  
Atmospheric Models ◽  
Period Range ◽  
Weather Forecasts ◽  
Atmospheric Disturbances ◽  
Medium Range ◽  
Model Improvement

<p>The uncertainties in the infrasound technology arise from the middle atmospheric disturbances, which are partly underrepresented in the atmospheric models such as in the European Centre for Medium-Range Weather Forecasts (ECMWF) products used for infrasound propagation simulations. In the framework of the ARISE (Atmospheric dynamics Research InfraStructure in Europe) project, multi-instrument observations are performed to provide new data sets for model improvement and future assimilations. In an unexpected way, new observations using the autonomous CORAL lidar showed significant differences between ECMWF analysis fields and observations in Argentina in the period range between 0.1 and 10 days. The model underestimates the wave activity, especially in the summer. During the same season, the infrasound bulletins of the IS02 station in Argentina indicate the presence of two prevailing directions of the detections, which are not reflected by the simulations. Observations at the Haute Provence Observatory (OHP) are used for comparison in different geophysical conditions. The origin of the observed anomalies are discussed in term of planetary waves effect on the infrasound propagation.</p>

scholarly journals Spatial and seasonal effects on the delayed ionospheric response to solar EUV changes

2019 ◽  
Author(s):  
Erik Schmölter ◽  
Jens Berdermann ◽  
Norbert Jakowski ◽  
Christoph Jacobi
Keyword(s):  
Southern Hemisphere ◽  
Geomagnetic Activity ◽  
Correlation Coefficients ◽  
Seasonal Effects ◽  
Constant Delay ◽  
Average Delay ◽  
Ionospheric Response ◽  
The Difference ◽  
Longitudinal Variability ◽  
The Impact

Abstract. This study correlates different ionospheric parameters with the integrated solar EUV radiation for an analysis of the delayed ionospheric response in order to confirm previous studies on the delay and to further specify variations of the delay. Several time series for correlation coefficients and delays are presented to characterize the trend of the delay from 2011 to 2013. The impact of the diurnal variations of ionospheric parameters in the analysis on hourly resolution for fixed locations are discussed and specified with calculations in different time scales and with comparison to solar and geomagnetic activity. An average delay for TEC of ≈ 18.7 hours and for foF2 of ≈ 18.6 hours is calculated at four European stations. Through comparison with the Australian region the difference between northern and southern hemisphere is analyzed and a seasonal variation of the delay between northern and southern hemisphere is calculated for TEC with ≈ 5 ± 0.7 hours and foF2 with ≈ 8 ± 0.8 hours. The latitudinal and longitudinal variability of the delay is analyzed for the European region and a decrease of the delay from ≈ 21.5 hours at 30° N to ≈ 19.0 hours at 70° N has been found. For winter months a roughly constant delay of ≈ 19.5 hours is calculated. In this study a North-South trend of the ionospheric delay during summer month has been observed with ≈ 0.06 hours per degree in latitude. The results based on solar and ionospheric data in hourly resolution and the analysis of the delayed ionospheric response to solar EUV show the seasonal and latitudinal variations. Results also indicate the dependence on the geomagnetic activity as well as on the 11-year solar cycle.

scholarly journals Choices in the Verification of S2S Forecasts and Their Implications for Climate Services

2020 ◽  
Vol 148 (10) ◽  
pp. 3995-4008
Author(s):  
Andrea Manrique-Suñén ◽  
Nube Gonzalez-Reviriego ◽  
Verónica Torralba ◽  
Nicola Cortesi ◽  
Francisco J. Doblas-Reyes
Keyword(s):  
Skill Score ◽  
Climate Services ◽  
Near Surface ◽  
Weather Forecasts ◽  
Probabilistic Evaluation ◽  
Skill Scores ◽  
Medium Range ◽  
The Impact ◽  
Start Dates

AbstractSubseasonal predictions bridge the gap between medium-range weather forecasts and seasonal climate predictions. This time scale is crucial for operations and planning in many sectors such as energy and agriculture. For users to trust these predictions and efficiently make use of them in decision-making, the quality of predicted near-surface parameters needs to be systematically assessed. However, the method to follow in a probabilistic evaluation of subseasonal predictions is not trivial. This study aims to offer an illustration of the impact that the verification setup might have on the calculation of the skill scores, thus providing some guidelines for subseasonal forecast evaluation. For this, several forecast verification setups to calculate the fair ranked probability skill score for tercile categories have been designed. These setups use different number of samples to compute the fair RPSS as well as different ways to define the climatology, characterized by different time periods to average (week or month). These setups have been tested by evaluating 2-m temperature in ECMWF-Ext-ENS 20-yr hindcasts for all of the initializations in 2016 against the ERA-Interim reanalysis. Then, the implications on skill score values of each of the setups are analyzed. Results show that to obtain a robust skill score several start dates need to be employed. It is also shown that a constant monthly climatology over each calendar month may introduce spurious skill score associated with the seasonal cycle. A weekly climatology bears similar results to a monthly running-window climatology; however, the latter provides a better reference climatology when bias adjustment is applied.

Climatology of Anticyclonic and Cyclonic Rossby Wave Breaking on the Dynamical Tropopause in the Southern Hemisphere

2011 ◽  
Vol 24 (4) ◽  
pp. 1239-1251 ◽  
Author(s):  
Jie Song ◽  
Chongyin Li ◽  
Jing Pan ◽  
Wen Zhou
Keyword(s):  
Southern Hemisphere ◽  
Rossby Wave ◽  
Zonal Wind ◽  
Potential Vorticity ◽  
Wave Breaking ◽  
Austral Summer ◽  
Austral Winter ◽  
Rossby Wave Breaking ◽  
Weather Forecasts ◽  
Medium Range

Abstract The characteristics of the climatological distribution of the anticyclonic (LC1) and cyclonic (LC2) Rossby wave breaking (RWB) in the Southern Hemisphere (SH) are investigated by calculating the occurrence frequency of the LC1- and LC2-like stratospheric potential vorticity (PV) streamers in the SH during the austral summer [December–February (DJF)] and wintertime [June–August (JJA)] on several isentropic surfaces by using the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) daily dataset. The results show that 1) on the equatorward flank of the climatological midlatitude jet (MLJ), the LC1-like PV streamers are frequently found over the central oceanic regions, whereas the LC2-like PV streamers are almost absent. On the poleward flank of the climatological MLJ, both types of PV streamers are frequently observed and the LC2-like PV streamers predominate; 2) the regions where the occurrences of the PV streamers are frequent overlap the weak zonal wind regions; and 3) in austral winter, a “double-jet” setting is evident in two regions of the SH [the double-jet upstream (DU) and the spilt jet region]. In the double-jet setting regions, the LC1-like PV streamers are frequently found both in the DU and the split-jet regions, while the occurrence of the LC2-like PV streamers is frequent in the split-jet region but is rather infrequent in the DU region.

scholarly journals Sensitivity, Structure, and Dynamics of Singular Vectors Associated with Hurricane Helene (2006)

2012 ◽  
Vol 69 (2) ◽  
pp. 675-694 ◽  
Author(s):  
Simon T. K. Lang ◽  
Sarah C. Jones ◽  
Martin Leutbecher ◽  
Melinda S. Peng ◽  
Carolyn A. Reynolds
Keyword(s):  
Three Dimensional ◽  
Growth Dynamics ◽  
Ensemble Forecasts ◽  
Weather Forecasts ◽  
Singular Vectors ◽  
Medium Range ◽  
Flow Features ◽  
Forecasting System ◽  
Diabatic Processes ◽  
The Impact

Abstract The sensitivity of singular vectors (SVs) associated with Hurricane Helene (2006) to resolution and diabatic processes is investigated. Furthermore, the dynamics of their growth are analyzed. The SVs are calculated using the tangent linear and adjoint model of the integrated forecasting system (IFS) of the European Centre for Medium-Range Weather Forecasts with a spatial resolution up to TL255 (~80 km) and 48-h optimization time. The TL255 moist (diabatic) SVs possess a three-dimensional spiral structure with significant horizontal and vertical upshear tilt within the tropical cyclone (TC). Also, their amplitude is larger than that of dry and lower-resolution SVs closer to the center of Helene. Both higher resolution and diabatic processes result in stronger growth being associated with the TC compared to other flow features. The growth of the SVs in the vicinity of Helene is associated with baroclinic and barotropic mechanisms. The combined effect of higher resolution and diabatic processes leads to significant differences of the SV structure and growth dynamics within the core and in the vicinity of the TC. If used to initialize ensemble forecasts with the IFS, the higher-resolution moist SVs cause larger spread of the wind speed, track, and intensity of Helene than their lower-resolution or dry counterparts. They affect the outflow of the TC more strongly, resulting in a larger downstream impact during recurvature. Increasing the resolution or including diabatic effects degrades the linearity of the SVs. While the impact of diabatic effects on the linearity is small at low resolution, it becomes large at high resolution.

Strong Trends in the Skill of the ERA-40 and NCEP–NCAR Reanalyses in the High and Midlatitudes of the Southern Hemisphere, 1958–2001*

2004 ◽  
Vol 17 (23) ◽  
pp. 4603-4619 ◽  
Author(s):  
David H. Bromwich ◽  
Ryan L. Fogt
Keyword(s):  
Satellite Data ◽  
Austral Winter ◽  
Weather Forecasts ◽  
Atmospheric Research ◽  
June July August ◽  
Medium Range ◽  
Height Fields ◽  
Environmental Prediction ◽  
June July ◽  
High Level

Abstract The European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis (NCEP1) data are compared with Antarctic and other mid- to high-latitude station observations for the complete years of overlap, 1958–2001. Overall, it appears that ERA-40 more closely follows the observations; however, a more detailed look at the presatellite era reveals many shortcomings in ERA-40, particularly in the austral winter. By calculating statistics in 5-yr moving windows for June–July–August (JJA), it is shown that ERA-40 correlations with observed MSLP and surface (2 m) temperatures are low and even negative during the mid-1960s. A significant trend in skill in ERA-40 is observed in conjunction with the assimilation of satellite data during winter, eventually reaching a high level of skill after 1978 that is superior to NCEP1. NCEP1 shows consistency in its correlation with observations throughout time in this season; however, the biases in the NCEP1 MSLP fields decrease significantly with time. Similar problems are also found in the 500-hPa geopotential height fields above the direct influences of the mountainous topography. The height differences between ERA-40 and NCEP1 over the South Pacific are substantial before the modern satellite era throughout the depth of the troposphere. The ability for ERA-40 to be more strongly constrained by the satellite data compared to NCEP1, which is largely constrained by the station observational network, suggests that the differing assimilation schemes between ERA-40 and NCEP1 lead to the large discrepancies seen here. Thus, both reanalyses must be used with caution over high southern latitudes during the nonsummer months prior to the assimilation of satellite sounding data.

scholarly journals Trajectory matching of ozonesondes and MOZAIC measurements in the UTLS – Part 2: Application to the global ozonesonde network

2014 ◽  
Vol 7 (1) ◽  
pp. 241-266 ◽  
Author(s):  
J. Staufer ◽  
J. Staehelin ◽  
R. Stübi ◽  
T. Peter ◽  
F. Tummon ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Data Sets ◽  
Wind Fields ◽  
Concentration Cell ◽  
Weather Forecasts ◽  
Long Term Stability ◽  
Medium Range ◽  
The Difference ◽  
Long Term Trend

Abstract. Both balloon-borne electrochemical ozonesondes and MOZAIC (measurements of ozone, water vapour, carbon monoxide and nitrogen oxides by in-service Airbus aircraft) provide very valuable data sets for ozone studies in the upper troposphere/lower stratosphere (UTLS). Although MOZAIC's highly accurate UV-photometers are regularly inspected and recalibrated annually, recent analyses cast some doubt on the long-term stability of their ozone analysers. To investigate this further, we perform a 16 yr comparison (1994–2009) of UTLS ozone measurements from balloon-borne ozonesondes and MOZAIC. The analysis uses fully three-dimensional trajectories computed from ERA-Interim (European Centre for Medium-Range Weather Forecasts Re-analysis) wind fields to find matches between the two measurement platforms. Although different sensor types (Brewer-Mast and Electrochemical Concentration Cell ozonesondes) were used, most of the 28 launch sites considered show considerable differences of up to 25% compared to MOZAIC in the mid-1990s, followed by a systematic tendency to smaller differences of around 5–10% in subsequent years. The reason for the difference before 1998 remains unclear, but observations from both sondes and MOZAIC require further examination to be reliable enough for use in robust long-term trend analyses starting before 1998. According to our analysis, ozonesonde measurements at tropopause altitudes appear to be rather insensitive to changing the type of the Electrochemical Concentration Cell ozonesonde, provided the cathode sensing solution strength remains unchanged. Scoresbysund (Greenland) showed systematically 5% higher readings after changing from Science Pump Corporation sondes to ENSCI Corporation sondes, while a 1.0% KI cathode electrolyte was retained.

The Efficiency of Upward Wave Propagation Near the Tropopause

2020 ◽  
Author(s):  
Israel Weinberger ◽  
Chaim Garfinkel ◽  
Thomas Birner
Keyword(s):  
Heat Flux ◽  
Wave Propagation ◽  
Index Of Refraction ◽  
Buoyancy Frequency ◽  
Median Percentage ◽  
Weather Forecasts ◽  
The Difference ◽  
The Impact ◽  
Positive Index ◽  
Anomalous Heat

<p>Recent work has highlighted that not all periods with anomalous heat flux at 100hPa were preceded by anomalous heat flux in the troposphere (Birner and Alberts 2017; White et al 2019; Camara et al 2019), and the goal of this work is to understand the factors that govern the efficiency of upward wave propagation near the tropopause. The index of refraction of Matsuno (1970) has been used to offer guidance on the direction of wave propagation within the stratosphere. Specifically, waves are preferentially refracted towards regions with a more positive index of refraction and ducted away from regions in which the index of refraction is more negative. However, the index of refraction was derived under the assumption that buoyancy frequency is constant at all height levels, which is clearly not true near the tropopause. This assumption allowed Matsuno to ignore certain height dependent buoyancy frequency terms, and here we explore the impact of these terms near the tropopause.</p><p>Using the dataset of the European Center for Medium-Range Weather Forecasts Reanalysis version 5 (ERA5) we defined 'transmitting' composites consisting of more efficient upward propagation events between 300hPa and 100hPa. Similarly, periods of less efficient upward propagation events between 300hPa and 100hPa are composited as 'decaying' events. We computed the index of refraction profile using a median, percentage of negative days and the trimmed mean (Wilks 2011), and also consider the terms neglected by Matsuno. We find that  the index of refraction can account for the difference between the decaying and transmitting composite.</p>

scholarly journals The Impact of Analysis Error on Medium-Range Weather Forecasts

2008 ◽  
Vol 136 (9) ◽  
pp. 3425-3431 ◽  
Author(s):  
Kyle L. Swanson ◽  
Paul J. Roebber
Keyword(s):  
North Pacific Ocean ◽  
Forecast Skill ◽  
Ensemble Spread ◽  
Weather Forecasts ◽  
The North ◽  
Medium Range ◽  
Difference Fields ◽  
Height Fields ◽  
Analysis Error ◽  
The Impact

Abstract All meteorological analyzed fields contain errors, the magnitude of which ultimately determines the point at which a given forecast will fail. Here, the authors explore the extent to which analysis difference fields capture certain aspects of the actual but unknowable flow-dependent analysis error. The analysis difference fields considered here are obtained by subtracting the NCEP and ECMWF reanalysis 500-hPa height fields. It is shown that the magnitude of this 500-hPa analysis difference averaged over the North Pacific Ocean has a statistically significant impact on forecast skill over the continental United States well into the medium range (5 days). Further, it is shown that the impact of this analysis difference on forecast skill is similar to that of ensemble spread well into the medium range, a measure of forecast uncertainty currently used in the operational setting. Finally, the analysis difference and ensemble spread are shown to be independent; hence, the impact of these two quantities upon forecast skill is additive.

scholarly journals An aerosol climatology for global models based on the tropospheric aerosol scheme in the Integrated Forecasting System of ECMWF

2019 ◽  
Author(s):  
Alessio Bozzo ◽  
Angela Benedetti ◽  
Johannes Flemming ◽  
Zak Kipling ◽  
Samuel Rémy
Keyword(s):  
Radiative Forcing ◽  
Regional Distribution ◽  
Atmospheric Composition ◽  
Monsoon Circulation ◽  
Weather Forecasts ◽  
Tropospheric Aerosol ◽  
Medium Range ◽  
Forecasting System ◽  
The Impact ◽  
Aerosol Radiative

Abstract. An aerosol climatology to represent aerosols in the radiation schemes of Global Atmospheric Models was recently developed. We derived the climatology from a reanalysis of atmospheric composition produced by the Copernicus Atmosphere Monitoring Service (CAMS). As an example of application into a global atmospheric model, we discuss the technical aspects of the implementation in the Integrated Forecasting System of European Centre for Medium Range Weather Forecasts (ECMWF-IFS) and the impact of the new climatology on the medium-range weather forecasts and one-year simulations. The new aerosol climatology was derived by combining a set of model simulation with constrained meteorological conditions and an atmospheric composition reanalysis for the period 2003–2014 produced by the IFS. The aerosol fields of the re-analysis are constrained by assimilating Aerosol optical thickness (AOT) retrievals product by the MODIS instruments. In a further step, we used modelled aerosol fields to correct the aerosol speciation and the vertical profiles of the aerosol reanalysis fields. The new climatology provides the monthly-mean mass mixing ratio of five aerosol species constrained by assimilated MODIS AOT. Using the new climatology in the ECMWF-IFS leads to changes in direct aerosol radiative effect compared to the climatology previously implemented, which have a small, but non-negligible impact on the forecast skill of large-scale weather patterns in the medium-range. However, details of the regional distribution of aerosol radiative forcing can have a large local impact. This is the case for the area of the Arabian Peninsula and the northern Indian Ocean. Here changes in the radiative forcing of the mineral dust significantly improve the Summer Monsoon circulation.

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