scholarly journals Investigation of dominant traveling 10-day wave components using long-term MERRA-2 database

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Chunming Huang ◽  
Wei Li ◽  
Shaodong Zhang ◽  
Gang Chen ◽  
Kaiming Huang ◽  
...  
Keyword(s):  
Flow Instability ◽  
Transmission Condition ◽  
Wave Number ◽  
Mean Flow ◽  
Excited Wave ◽  
Propagating Waves ◽  
Zonal Wave Number ◽  
The Mean

AbstractThe eastward- and westward-traveling 10-day waves with zonal wavenumbers up to 6 from surface to the middle mesosphere during the recent 12 years from 2007 to 2018 are deduced from MERRA-2 data. On the basis of climatology study, the westward-propagating wave with zonal wave number 1 (W1) and eastward-propagating waves with zonal wave numbers 1 (E1) and 2 (E2) are identified as the dominant traveling ones. They are all active at mid- and high-latitudes above the troposphere and display notable month-to-month variations. The W1 and E2 waves are strong in the NH from December to March and in the SH from June to October, respectively, while the E1 wave is active in the SH from August to October and also in the NH from December to February. Further case study on E1 and E2 waves shows that their latitude–altitude structures are dependent on the transmission condition of the background atmosphere. The presence of these two waves in the stratosphere and mesosphere might have originated from the downward-propagating wave excited in the mesosphere by the mean flow instability, the upward-propagating wave from the troposphere, and/or in situ excited wave in the stratosphere. The two eastward waves can exert strong zonal forcing on the mean flow in the stratosphere and mesosphere in specific periods. Compared with E2 wave, the dramatic forcing from the E1 waves is located in the poleward regions.

A Novel Vibrating Ribbon Technique

2005 ◽  
Author(s):  
Jonathan H. Watmuff
Keyword(s):  
Test Section ◽  
Vibration Amplitude ◽  
Wave Amplitude ◽  
Separation Bubble ◽  
Wind Tunnel Test ◽  
Mean Flow ◽  
Test Plate ◽  
Numerical Predictions ◽  
The Mean

A novel vibrating ribbon apparatus is described that is active over the full span of a wind tunnel test section. The spanwise uniformity of the vibration amplitude and other ribbon characteristics are considered in detail. The height of each end of the ribbon above the test plate can be adjusted in situ, while the ribbon is vibrating and with flow in the test section, thereby allowing the response of the layer to be easily tuned. The growth of the wave amplitude downstream of the ribbon is shown to agree with numerical predictions. However, two or three wavelengths of development are required before the wave amplitude follows the predicted growth. The flow around an inactive ribbon is examined using a commercial CFD solver and features such as a miniature separation bubble just downstream of the ribbon are revealed. The distance required for the mean flow to recover from the disturbance introduced by the ribbon is greater when the ribbon is located further from the wall. The mean flow recovers to form a boundary layer that is slightly thicker than the undisturbed flow. Experimental measurements indicate that the distance required for the wave motions to follow predicted behavior is about 4 or 5 times larger than distance for recovery of the mean flow.

scholarly journals Climatic variability of the mean flow and stationary planetary waves in the NCEP/NCAR reanalysis data

2008 ◽  
Vol 26 (5) ◽  
pp. 1233-1241 ◽  
Author(s):  
A. Yu. Kanukhina ◽  
E. V. Suvorova ◽  
L. A. Nechaeva ◽  
E. K. Skrygina ◽  
A. I. Pogoreltsev
Keyword(s):  
Lower Stratosphere ◽  
Climatic Variability ◽  
Reanalysis Data ◽  
Planetary Waves ◽  
Lower Atmosphere ◽  
Wave Number ◽  
Mean Flow ◽  
The Mean ◽  
The 1960S ◽  
Environmental Prediction

Abstract. NCEP/NCAR (National Center for Environmental Prediction – National Center for Atmospheric Research) data have been used to estimate the long-term variability of the mean flow, temperature, and Stationary Planetary Waves (SPW) in the troposphere and lower stratosphere. The results obtained show noticeable climatic variabilities in the intensity and position of the tropospheric jets that are caused by temperature changes in the lower atmosphere. As a result, we can expect that this variability of the mean flow will cause the changes in the SPW propagation conditions. The simulation of the SPW with zonal wave number m=1 (SPW1), performed with a linearized model using the mean flow distributions typical for the 1960s and for the beginning of 21st century, supports this assumption and shows that during the last 40 years the amplitude of the SPW1 in the stratosphere and mesosphere increased substantially. The analysis of the SPW amplitudes extracted from the geopotential height and zonal wind NCEP/NCAR data supports the results of simulation and shows that during the last years there exists an increase in the SPW1 activity in the lower stratosphere. These changes in the amplitudes are accompanied by increased interannual variability of the SPW1, as well. Analysis of the SPW2 activity shows that changes in its amplitude have a different sign in the northern winter hemisphere and at low latitudes in the southern summer hemisphere. The value of the SPW2 variability differs latitudinally and can be explained by nonlinear interference of the primary wave propagation from below and from secondary SPW2.

scholarly journals The quasi-two-day wave studied using the Northern Hemisphere SuperDARN HF radars

2007 ◽  
Vol 25 (8) ◽  
pp. 1767-1778 ◽  
Author(s):  
S. B. Malinga ◽  
J. M. Ruohoniemi
Keyword(s):  
Northern Hemisphere ◽  
Spectral Power ◽  
Auroral Zone ◽  
Meridional Flow ◽  
Wave Activity ◽  
Wave Number ◽  
Strongly Correlated ◽  
Mean Flow ◽  
Abstract Data ◽  
Zonal Wave Number

Abstract. Data from the Super Dual Radar Network (SuperDARN) radars for 2002 were used to study the behaviour of the quasi-two-day wave (QTDW) in the Northern Hemisphere auroral zone. The period of the QTDW is observed to vary in the range of ~42–56 h, with the most dominant period being ~48 h and secondary peaks at ~42- and ~52-h. The spectral power shows a seasonal variation with a peak power (max~70) in summer. The power shows variations of several days and there is also evidence of changes in wave strength with longitude. The 42-h and the 48-h components tend to be strongly correlated in summer. The onset of enhanced wave activity tends to coincide with the westward acceleration of the zonal mean flow and occurs at a time of strong southward meridional flow. The most frequent instantaneous hourly period is in the 40 to 50 h period band, in line with the simultaneous dominance of the 42-h and the 48-h components. The wave numbers are less variable and are around −2 to −4 during times of strong wave activity. For a period of ~48 h, the zonal wave number is about −3 to −4, using a negative value to indicate westward propagating waves. The 42-h and the 52-h components cover a wider band in the −4 to 1 range. The wide zonal wave number spectrum in our results may account for the observed longitudinal variation in the spectral power of the wave.

The wave modes in ducted swirling flows

1998 ◽  
Vol 371 ◽  
pp. 1-20 ◽  
Author(s):  
CHRISTOPHER K. W. TAM ◽  
LAURENT AURIAULT
Keyword(s):  
Swirling Flow ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Inviscid Flow ◽  
Mean Flow ◽  
Compressibility Effect ◽  
Propagating Waves ◽  
The Mean ◽  
Initial Boundary Value ◽  
Wave Modes

The small-amplitude wave modes inside a ducted inviscid compressible swirling flow are investigated. In order to avoid possible mathematical ambiguities arising from the use of an inviscid flow model, the wave modes are cast as the solution of an initial boundary value problem. Two families of propagating waves are found. The acoustic modes are supported by the compressibility effect of the flow. The rotational modes are sustained by the centrifugal force field associated with the mean flow rotation. Two cases, one with a free-vortex swirl and the other with a rigid-body swirl, are investigated in some depth. Numerical results are provided.

scholarly journals Characterization of the long-term radiosonde temperature biases in the upper troposphere and lower stratosphere using COSMIC and Metop-A/GRAS data from 2006 to 2014

2017 ◽  
Vol 17 (7) ◽  
pp. 4493-4511 ◽  
Author(s):  
Shu-peng Ho ◽  
Liang Peng ◽  
Holger Vömel
Keyword(s):  
Lower Stratosphere ◽  
Temperature Measurements ◽  
Climate Data ◽  
Upper Troposphere ◽  
Global Trend ◽  
The Mean ◽  
Temperature Climate

Abstract. Radiosonde observations (RAOBs) have provided the only long-term global in situ temperature measurements in the troposphere and lower stratosphere since 1958. In this study, we use consistently reprocessed Global Positioning System (GPS) radio occultation (RO) temperature data derived from the COSMIC and Metop-A/GRAS missions from 2006 to 2014 to characterize the inter-seasonal and interannual variability of temperature biases in the upper troposphere and lower stratosphere for different radiosonde sensor types. The results show that the temperature biases for different sensor types are mainly due to (i) uncorrected solar-zenith-angle-dependent errors and (ii) change of radiation correction. The mean radiosonde–RO global daytime temperature difference in the layer from 200 to 20 hPa for Vaisala RS92 is equal to 0.20 K. The corresponding difference is equal to −0.06 K for Sippican, 0.71 K for VIZ-B2, 0.66 K for Russian AVK-MRZ, and 0.18 K for Shanghai. The global daytime trend of differences for Vaisala RS92 and RO temperature at 50 hPa is equal to 0.07 K/5 yr. Although there still exist uncertainties for Vaisala RS92 temperature measurement over different geographical locations, the global trend of temperature differences between Vaisala RS92 and RO from June 2006 to April 2014 is within ±0.09 K/5 yr. Compared with Vaisala RS80, Vaisala RS90, and sondes from other manufacturers, the Vaisala RS92 seems to provide the most accurate RAOB temperature measurements, and these can potentially be used to construct long-term temperature climate data records (CDRs). Results from this study also demonstrate the feasibility of using RO data to correct RAOB temperature biases for different sensor types.

On the mean motion induced by internal gravity waves

1969 ◽  
Vol 36 (4) ◽  
pp. 785-803 ◽  
Author(s):  
Francis P. Bretherton
Keyword(s):  
Gravity Waves ◽  
Wave Energy ◽  
Wave Train ◽  
Three Dimensional ◽  
Internal Gravity Waves ◽  
Wave Number ◽  
Mean Flow ◽  
Mean Velocity ◽  
Mean Motion ◽  
The Mean

A train of internal gravity waves in a stratified liquid exerts a stress on the liquid and induces changes in the mean motion of second order in the wave amplitude. In those circumstances in which the concept of a slowly varying quasi-sinusoidal wave train is consistent, the mean velocity is almost horizontal and is determined to a first approximation irrespective of the vertical forces exerted by the waves. The sum of the mean flow kinetic energy and the wave energy is then conserved. The circulation around a horizontal circuit moving with the mean velocity is increased in the presence of waves according to a simple formula. The flow pattern is obtained around two- and three-dimensional wave packets propagating into a liquid at rest and the results are generalized for any basic state of motion in which the internal Froude number is small. Momentum can be associated with a wave packet equal to the horizontal wave-number times the wave energy divided by the intrinsic frequency.

scholarly journals Investigation on the abnormal quasi-two day wave activities during sudden stratospheric warming period of January 2006

2017 ◽  
Author(s):  
Sheng-Yang Gu ◽  
Xiankang Dou ◽  
Dora Pancheva
Keyword(s):  
Planetary Wave ◽  
Phase Speed ◽  
Dominant Mode ◽  
Wave Number ◽  
Stratospheric Warming ◽  
Mean Flow ◽  
Sudden Stratospheric Warming ◽  
Reanalysis Dataset ◽  
Short Period ◽  
Zonal Wave Number

Abstract. The quasi-two day wave (QTDW) during austral summer period usually coincides with sudden stratospheric warming (SSW) event in the winter hemisphere, while the influences of SSW on QTDW are not totally understood. In this work, the anomalous QTDW activities during the major SSW period of January 2006 are further investigated on the basis of hourly Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude (NOGAPS-ALPHA) reanalysis dataset. Strong westward QTDW with zonal wave number 2 (W2) is identified besides the conventionally dominant mode of zonal wave number 3 (W3). Meanwhile, the W3 peaks with an extremely short period of ~ 42 hours. Compared with January 2005 with no evident SSW, we found that the zonal mean zonal wind in the summer mesosphere is enhanced during 2006. The enhanced summer easterly sustains critical layers for W2 and short-period W3 QTDWs with larger phase speed, which facilitate their amplification through wave-mean flow interaction. The stronger summer easterly also provides stronger barotropic/baroclinic instabilities and thus larger forcing for the amplification of QTDW. The inter-hemispheric coupling induced by strong winter stratospheric planetary wave activities during SSW period is most likely responsible for the enhancement of summer easterly. Besides, we found that the nonlinear interaction between W3 QTDW and the wave number 1 stationary planetary wave (SPW1) may also contribute to the source of W2 at middle and low latitudes in the mesosphere.

scholarly journals Impacts of mean dynamic topography on a regional ocean assimilation system

Ocean Science ◽  
2015 ◽  
Vol 11 (5) ◽  
pp. 829-837 ◽  
Author(s):  
C. Yan ◽  
J. Zhu ◽  
C. A. S. Tanajura
Keyword(s):  
Data Assimilation ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Dynamic Topography ◽  
Altimetry Data ◽  
Mean Dynamic Topography ◽  
Mean Sea Surface ◽  
The Mean

Abstract. An ocean data assimilation system was developed for the Pacific–Indian oceans with the aim of assimilating altimetry data, sea surface temperature, and in situ measurements from Argo (Array for Real-time Geostrophic Oceanography), XBT (expendable bathythermographs), CTD (conductivity temperature depth), and TAO (Tropical Atmosphere Ocean). The altimetry data assimilation requires the addition of the mean dynamic topography to the altimetric sea level anomaly to match the model sea surface height. The mean dynamic topography is usually computed from the model long-term mean sea surface height, and is also available from gravimetric satellite data. In this study, the impact of different mean dynamic topographies on the sea level anomaly assimilation is examined. Results show that impacts of the mean dynamic topography cannot be neglected. The mean dynamic topography from the model long-term mean sea surface height without assimilating in situ observations results in worsened subsurface temperature and salinity estimates. Even if all available observations including in situ measurements, sea surface temperature measurements, and altimetry data are assimilated, the estimates are still not improved. This proves the significant impact of the MDT (mean dynamic topography) on the analysis system, as the other types of observations do not compensate for the shortcoming due to the altimetry data assimilation. The gravimeter-based mean dynamic topography results in a good estimate compared with that of the experiment without assimilation. The mean dynamic topography computed from the model long-term mean sea surface height after assimilating in situ observations presents better results.

scholarly journals Characterization of the Long-term Radiosonde Temperature Biases in the Lower Stratosphere using COSMIC and Metop-A/GRAS Data from 2006 to 2014

2016 ◽  
Author(s):  
Shu-Peng Ho ◽  
Liang Peng ◽  
Holger Vömel
Keyword(s):  
Global Positioning System ◽  
Lower Stratosphere ◽  
Temperature Measurements ◽  
Global Trend ◽  
Global Positioning ◽  
The Mean ◽  
Geographical Locations

Abstract. Radiosonde observations (RAOBs) have provided the only long-term global in situ temperature measurements in the troposphere and lower stratosphere since 1958. In this study, we use consistently reprocessed Global Positioning System (GPS) radio occultation (RO) temperature data derived from COSMIC and Metop-A/GRAS missions from 2006 to 2014 to characterize the inter-seasonal and inter-annual variability of temperature biases in the lower stratosphere for different sensor types. The results show that the RAOB temperature biases for different RAOB sensor types are mainly owing to i) uncorrected solar zenith angle dependent errors, and ii) change of radiation correction. The mean daytime temperature difference (ΔT) for Vaisala RS92 is equal to 0.18 K in Australia, 0.20 K in Germany, 0.10 K in Canada, 0.13 K in England, and 0.33 K in Brazil. The mean daytime ΔT is equal to −0.06 K for Sippican, 0.71 K for VIZ-B2, 0.66 K for AVK-MRZ, and 0.18 K for Shanghai. The daytime trend of anomalies for Vaisala RS92 and RO temperature at 50 hPa is equal to 0.00 K/5 yrs over United States, −0.02 K/5 yrs over Germany, 0.17 K/5 yrs over Australia, 0.23 K/5 yrs over Canada, 0.26 K/5 yrs over England, and 0.12 K/5 yrs over Brazil, respectively. Although there still exist uncertainties for Vaisala RS92 temperature measurements over different geographical locations, the global trend of temperature anomaly between Vaisala RS92 and RO from June 2006 to April 2014 is within +/−0.09 K/5 yrs globally. Comparing with Vaisala RS80, Vaisala RS90 and sondes from other manufacturers, the Vaisala RS92 seems to provide the best RAOB temperature measurements, which can potentially be used to construct long term temperature CDRs. Results from this study also demonstrate the feasibility to use RO data to correct RAOB temperature biases for different sensor types.

scholarly journals Comparative study on long term climate data sources over South Korea

2018 ◽  
Vol 10 (3) ◽  
pp. 504-523 ◽  
Author(s):  
Dong-Ik Kim ◽  
Dawei Han
Keyword(s):  
South Korea ◽  
Climate Impact ◽  
Climate Data ◽  
The World ◽  
In Situ Observations ◽  
The Mean ◽  
Global Datasets ◽  
Different Parts

Abstract Long term climate data are vitally important in reliably assessing water resources and water related hazards, but in-situ observations are generally sparse in space and limited in time. Although there are several global datasets available as substitutes, there is a lack of comparative studies about their suitability in different parts of the world. In this study, to find out the reliable century-long climate dataset in South Korea, we first evaluate multi-decadal reanalyses (ERA-20 cm, ERA-20c, ERA-40 and NOAA 20th century reanalysis (20CR)) and gridded observations (CRUv3.23 and GPCCv7) for monthly mean precipitation and temperature. In the temporal and statistical comparisons, CRUv3.23 and GPCCv7 for precipitation and ERA-40 for temperature perform the best, and ERA-20c and 20CR also indicate meaningful agreements. For ERA-20 cm, it has only a statistical agreement, but the mean has the difficulty in representing its ensemble. This paper also shows that the applicability of each dataset may vary by region and all products should be locally adjusted before being applied in climate impact assessments. These findings not only help to fill in the knowledge gaps about these datasets in South Korea but also provide a useful guideline for the applicability of the global datasets in different parts of the world.

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