scholarly journals A Northern Hemispheric climatology of indices for clear air turbulence in the tropopause region derived from ERA40 reanalysis data

2007 ◽  
Vol 112 (D20) ◽  
Author(s):  
E. B. Jaeger ◽  
M. Sprenger
Keyword(s):  
Reanalysis Data ◽  
Era40 Reanalysis ◽  
Air Turbulence ◽  
Tropopause Region ◽  
Northern Hemispheric

scholarly journals Loss of Significance and Multidecadal Variability of the Madden–Julian Oscillation

2010 ◽  
Vol 23 (13) ◽  
pp. 3739-3751 ◽  
Author(s):  
E. Suhas ◽  
B. N. Goswami
Keyword(s):  
Kinetic Energy ◽  
Energy Exchange ◽  
Reanalysis Data ◽  
Long Waves ◽  
Mean Flow ◽  
Multidecadal Variability ◽  
Rate Of Increase ◽  
Increasing Trend ◽  
Northern Hemispheric ◽  
Data Variation

Abstract Change in significance and multidecadal variability of the Northern Hemispheric winter MJO during 1948–2006 is examined using NCEP–NCAR reanalysis data. Variation of the MJO power relative to a red background is estimated by isolating the MJO signal through frequency–wavenumber spectral analysis using a 10-yr sliding window. It is shown that during the period of study, the rate of increase of background power has been larger than the rate of increase of the MJO power, leading to a decreasing trend of significant MJO power. It is also found that a multidecadal variation rides on the decreasing trend of significant power of the MJO. Another finding is that the zonal mean component of the zonal wind at 200 hPa on a MJO time scale has a significant increasing trend. Both of the above trends are statistically significant at the 95% confidence level. Energetics calculations in the wavenumber domain were carried out to understand why the significant MJO power is not increasing as fast as the red background. It is shown that long waves (wavenumbers 1–3, i.e., the MJO scale) lose energy to the zonal mean flow and the rate of kinetic energy gain by the zonal mean flow from the long waves has a linear increasing trend. Thus, while the MJO is also being energized by a warming ocean, it is losing increasingly more energy to the zonal mean flow, making the zonal mean more energetic while losing its own significance at the same time. It is found that the observed multidecadal variability of the significant MJO power has no relationship with other well-known multidecadal variability. However, the authors find that the multidecadal variability of the MJO and the rate of kinetic energy exchange between the zonal mean flow and long waves are closely linked, indicating that the observed multidecadal variability of the MJO is internally driven.

scholarly journals Comparison of IAGOS in-situ water vapour measurements and ECMWF ERA-Interim Reanalysis data

2019 ◽  
Author(s):  
Philipp Reutter ◽  
Patrick Neis ◽  
Susanne Rohs ◽  
Bastien Sauvage
Keyword(s):  
Water Vapour ◽  
Spatial Resolution ◽  
Three Dimensional ◽  
Reanalysis Data ◽  
Cirrus Clouds ◽  
Data Sets ◽  
The North ◽  
Tropopause Region ◽  
Good Agreement

Abstract. Cirrus clouds and their potential formation regions, so-called ice-supersaturated regions (ISSRs) occur frequently in the tropopause region. It is assumed that ISSRs and cirrus clouds can change the tropopause structure by diabatic processes, driven by latent heating due to phase transition and interaction with radiation. For many research questions a three-dimensional picture including a sufficient temporal resolution of the water vapour fields in the tropopause region is required. This requirement is fulfilled nowadays by reanalysis products such as the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis. However, for a meaningful investigation of water vapour in the tropopause region a comparison of the reanalysis data with measurement is advisable, since it is difficult to measure water vapour and to assimilate meaningful measurements into reanalysis products. Here, we present an intercomparison of high-resolution in-situ measurements aboard passenger aircraft within the European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System; http://www.iagos.org) with ERA-Interim. Temperature and humidity data over the North Atlantic from 2000 to 2010 are compared relative to the dynamical tropopause. The comparison of the temperature shows a good agreement between measurement and ERA-Interim. While ERA-Interim can reproduce the main features of the water vapour measurements of IAGOS, the variability of the data is underestimated by the reanalysis data. The combination of temperature and water vapour leads to the relative humidity with respect to ice (RHi). Here ERA-Interim deviates from the measurements concerning values of larger than RHi=100 %, both in number and strength of supersaturation. The comparison of ISSR pathlengths shows distinct differences, which can be traced back to the spatial resolution of both data sets. IAGOS shows significantly more smaller ISSRs compared to ERA-Interim. A good agreement begins only at pathlengths in the order of the ERA-Interim spatial resolution and larger.

scholarly journals SPATIAL AND TIME CHANGES IN CLIMATIC CHARACTERISTICS IN THE TROPO-STRATOSPHERE IN THE NORTH-WEST OF THE VOLGA FEDERAL DISTRICT

2020 ◽  
Vol 30 (4) ◽  
pp. 448-456
Author(s):  
M.A. Myagkov
Keyword(s):  
Lower Troposphere ◽  
Ground Level ◽  
Federal District ◽  
Reanalysis Data ◽  
Linear Temperature ◽  
Mean Values ◽  
North West ◽  
The North ◽  
Tropopause Region ◽  
Time Changes

The spatial-temporal changes in the thermal regime with a spatial resolution of 0.25×0.25° in the north-west of the Volga Federal District were considered according to the ERA5 reanalysis data for the period 1979-2018 To study the altitude distribution of air temperature, vertical profiles of mean values, standard deviation and slope coefficient of the linear temperature trend were constructed on 37 isobaric surfaces from ground level to 47 km (1 hPa), and the coefficients of determination were calculated. Determined the degree of correlations between adjacent levels the tropo-stratosphere in the temperature field by seasons and in general for the year, its significant weakening in the tropopause region was revealed. The time tendency of temperature rise in the lower troposphere and its decrease in the stratosphere is revealed.

scholarly journals Dehydration and low ozone in the tropopause layer over the Asian monsoon caused by tropical cyclones: Lagrangian transport calculations using ERA-Interim and ERA5 reanalysis data

2019 ◽  
Author(s):  
Dan Li ◽  
Bärbel Vogel ◽  
Rolf Müller ◽  
Jianchun Bian ◽  
Gebhard Günther ◽  
...  
Keyword(s):  
Water Vapour ◽  
Tropical Cyclones ◽  
Asian Summer Monsoon ◽  
Deep Convection ◽  
Reanalysis Data ◽  
Western Pacific ◽  
Lagrangian Model ◽  
Trajectory Calculations ◽  
Tropopause Region ◽  
The Western Pacific

Abstract. Low ozone and low water vapour values near the tropopause over Kunming, China were observed using balloon-borne measurements performed during the SWOP (sounding water vapour, ozone, and particle) campaign in August 2009 and 2015. Here, we investigate low ozone and water vapour signatures in the upper troposphere and lower stratosphere (UTLS) using FengYun-2D, FengYun-2G, Aura Microwave Limb Sounder (MLS) satellite measurements and backward trajectory calculations driven by both ERA-Interim and ERA5 reanalysis data. Trajectories with kinematic and diabatic vertical velocities were calculated using the Chemical Lagrangian Model of the Stratosphere (CLaMS) trajectory module. All trajectory calculations show that air parcels with low ozone and low water vapour values in the UTLS over Kunming measured by balloon-borne instruments originate from the western Pacific boundary layer. Deep convection associated with tropical cyclones over the western Pacific transports boundary air parcels with low ozone into the cold tropopause region. Subsequently, these air parcels are mixed into the strong easterlies on the southern side of the Asian summer monsoon anticyclone. Air parcels are dehydrated when passing the lowest temperature region (

scholarly journals Global temperature estimates in the troposphere and stratosphere: a validation study of COSMIC/FORMOSAT-3 measurements

2009 ◽  
Vol 9 (3) ◽  
pp. 897-908 ◽  
Author(s):  
P. Kishore ◽  
S. P. Namboothiri ◽  
J. H. Jiang ◽  
V. Sivakumar ◽  
K. Igarashi
Keyword(s):  
Validation Study ◽  
Radio Occultation ◽  
Reanalysis Data ◽  
First Year ◽  
Data Sets ◽  
Tropical Tropopause ◽  
The United Kingdom ◽  
Tropopause Region ◽  
Environmental Prediction ◽  
Good Agreement

Abstract. This paper mainly focuses on the validation of temperature estimates derived with the newly launched Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC)/Formosa Satellite 3 (FORMOSAT-3) system. The analysis is based on the radio occultation (RO) data samples collected during the first year observation from April 2006 to April 2007. For the validation, we have used the operational stratospheric analyses including the National Centers for Environmental Prediction - Reanalysis (NCEP), the Japanese 25-year Reanalysis (JRA-25), and the United Kingdom Met Office (MetO) data sets. Comparisons done in different formats reveal good agreement between the COSMIC and reanalysis outputs. Spatially, the largest deviations are noted in the polar latitudes, and height-wise, the tropical tropopause region noted the maximum differences (2–4 K). We found that among the three reanalysis data sets the NCEP data sets have the best resemblance with the COSMIC measurements.

scholarly journals Instability and its relation to precipitation over the Eastern Iberian Peninsula

2007 ◽  
Vol 10 ◽  
pp. 45-50 ◽  
Author(s):  
I. Iturrioz ◽  
E. Hernández ◽  
P. Ribera ◽  
S. Queralt
Keyword(s):  
Iberian Peninsula ◽  
Reanalysis Data ◽  
Radiosonde Data ◽  
Dynamical Instability ◽  
Era40 Reanalysis ◽  
Stratiform Precipitation ◽  
Palma De Mallorca ◽  
Thermodynamic Instability ◽  
Q Vector ◽  
Instability Indices

Abstract. Synoptic situations producing rainfall at four rawinsonde observatories at eastern Spain are classified as stratiform or convective depending on dynamic and thermodynamic instability indices. Two daily radiosonde and daily-accumulated precipitation data from four observatories in Eastern Spain are used: Madrid-Barajas (MB), Murcia (MU), Palma de Mallorca (PA) and Zaragoza (ZA). We calculated two thermodynamic instability indices from radiosonde data: CAPE and LI. Likewise, from ERA40 reanalysis data we have calculated the Q vector divergence over the Iberian Peninsula and Balearic Islands, as a parameter describing dynamical instability. Synoptic situations producing rainfall were classified as convective or stratiform, satisfying a criterion based on the values of dynamic and thermodynamic indices at each observatory. It is observed that the number of days with stratiform precipitation related to the total number of precipitation days follows a consistent annual pattern.

scholarly journals Estimation of the systematic error of precipitation and humidity in the MM5 model

2008 ◽  
Vol 16 ◽  
pp. 97-107 ◽  
Author(s):  
S. Ivanov ◽  
C. Simmer ◽  
J. Palamarchuk ◽  
S. Bachner
Keyword(s):  
Reanalysis Data ◽  
Model Errors ◽  
Atmospheric Flow ◽  
Parameterization Schemes ◽  
The North ◽  
Era40 Reanalysis ◽  
Mm5 Model ◽  
Model Parameterization ◽  
Geographical Regions ◽  
Microphysical Processes

Abstract. To comprehensively diagnose model capabilities in simulating atmospheric flow including the relevant microphysical processes, the main prognostic fields of the MM5 model are compared with ERA40 reanalysis data. This approach allows to identify and compare meaningful features of model parameterization schemes and to quantify model errors. Various combinations of schemes for cumulus convection, planetary boundary layer (PBL), microphysics and radiative transfer are used in order to identify those combinations which produce the closest resemblance between model state and reanalysis. The spatial structure of systematic errors, both horizontal and vertical will be described and geographical regions and synoptic situations will be identified, which are associated with pronounced systematic model deviations. The study focused on precipitation and humidity fields as well as on the main thermodynamic atmospheric variables on a coarse resolution grid (about 80 km) over the North Atlantic - Europe region. Our results identify advantages and shortcomings of the various parameterization schemes. They also indicate that, in general, the combination of best schemes does not result in optimal simulations of a particular variable.

scholarly journals Aerosol effects on clouds and precipitation during the 1997 smoke episode in Indonesia

2007 ◽  
Vol 7 (6) ◽  
pp. 17099-17116 ◽  
Author(s):  
H.-F. Graf ◽  
J. Yang ◽  
T. M. Wagner
Keyword(s):  
Large Scale ◽  
Convective Cloud ◽  
Reanalysis Data ◽  
Cumulus Parameterization ◽  
Convective Precipitation ◽  
Limited Area ◽  
High Background ◽  
Convective Clouds ◽  
Era40 Reanalysis ◽  
Instability Energy

Abstract. In 1997/98 a severe smoke episode due to extensive biomass burning, especially of peat, was observed over Indonesia. September 1997 was the month with the highest aerosol burden. This month was simulated using the limited area model REMOTE driven at its lateral boundaries by ERA40 reanalysis data. REMOTE was extended by a new convective cloud parameterization mimicking individual clouds competing for instability energy. This allows for the interaction of aerosols and convective clouds and precipitation. Results show that convective precipitation is diminished at all places with high aerosol loading, but at some areas with high background humidity precipitation from large-scale clouds may over-compensate the loss in convective rainfall. At individual time steps, very few cases were found when polluted convective clouds produced intensified rainfall via mixed phase microphysics. However, these cases are not unequivocal and opposite results were also simulated, indicating that other than aerosol-microphysics effects have important impact on the results. Overall, the introduction of the new cumulus parameterization and of aerosol-cloud interaction improved the simulation of precipitation patterns and total amount.

scholarly journals On the occurrence of enhanced vertical wind shear in the tropopause region: A ten year ERA5 northern hemispheric study

2021 ◽  
Author(s):  
Thorsten Kaluza ◽  
Daniel Kunkel ◽  
Peter Hoor
Keyword(s):  
Wind Shear ◽  
Lower Thermosphere ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Occurrence Frequency ◽  
Lapse Rate ◽  
Jet Stream ◽  
Linear Wave ◽  
Tropopause Region ◽  
Northern Hemispheric

Abstract. A climatology of the occurrence of enhanced wind shear in the UTLS is presented, which gives rise to define a tropopause shear layer (TSL). Enhanced wind shear in the tropopause region is of interest because it can generate turbulence which can lead to cross-tropopause mixing. The analysis is based on ten years of daily northern hemispheric ECMWF ERA-5 reanalysis data. The vertical extent of the region analysed is limited to the altitudes from 1.5 km above the surface up to 25 km, to exclude the planetary boundary layer as well as enhanced wind shear in higher atmospheric layers like the mesosphere/lower thermosphere. A threshold value of S2t = 4 · 10−4 s−2 is applied, which marks the top end of the spectrum of atmospheric wind shear to focus on situations which cannot be sustained by the mean static stability in the troposphere according to linear wave theory. This subset of the vertical wind shear spectrum is analysed for its vertical, geographical, and seasonal occurrence frequency distribution. A set of metrics is defined to narrow down the relation to planetary circulation features, as well as indicators for momentum gradient sharpening mechanisms. The vertical distribution reveals that large shear values occur almost exclusively at tropopause altitudes, within a vertically confined layer of about 1–2 km extent directly above the local lapse rate tropopause (LRT). The TSL emerges as a distinct feature in the tropopause-based 10 year temporal and zonal mean climatology, spanning from the tropics to latitudes around 70° N, with average occurrence frequencies of the order of 1 %–10 %. The horizontal distribution of the tropopause based enhanced vertical wind shear exhibits distinctly separated regions of occurrence, which are generally associated with jet streams and their seasonality. At midlatitudes, enhanced wind shear values occur most frequently in regions with an elevated tropopause and at latitudes around 50° N, associated with jet streaks within northward reaching ridges of baroclinic waves. At lower latitudes in the region of the subtropical jet stream, which is mainly apparent over the East Asian continent, the occurrence frequency of enhanced tropopause-based wind shear reaches maximum values of about 30 % during winter and is tightly linked to the jet stream seasonality. The interannual variability of the occurrence frequency for enhanced wind shear might furthermore be linked to the variability of the zonal location and strength of the jet. The east-equatorial region features a bi-annual seasonality in the occurrence frequencies of tropopause based enhanced vertical wind shear. During the summer months, large areas of the tropopause region over the Indian ocean are up to 70 % of the time exposed to large values of wind shear, which can be attributed to the emergence of the tropical easterly jet. During winter, this occurrence frequency maximum shifts eastward over the maritime continent, where it is exceptionally pronounced during the 2011 la Niña year, as well as quite weak during the El Niño phases of 2010 and 2015/2016. This agrees with the atmospheric response of the Pacific Walker circulation cell in the ENSO ocean-atmosphere coupling.

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