scholarly journals Intra-seasonal variation of surface air temperature in Nepal Himalayas

MAUSAM ◽  
2022 ◽  
Vol 53 (3) ◽  
pp. 281-288
Author(s):  
KENICHI UENO ◽  
ADARSHA P. POKHREL
Keyword(s):  
Seasonal Variation ◽  
Air Temperature ◽  
Monsoon Season ◽  
Surface Air Temperature ◽  
Circulation Pattern ◽  
Synoptic Scale ◽  
Local Circulation ◽  
Pressure System ◽  
Surface Temperature Variation ◽  
Unique Surface

Intra-seasonal variation of surface air temperature observed by the automatic weather station at Syangpoche in Khumbu region, Nepal Himalayas, is analyzed.  In the monsoon season, temperature was nearly constant with large decrease in insolation due to monsoon clouds.  On the other hand, large intra-seasonal variation existed in the winter with increase in temperature associated with passing synoptic scale high-pressure system which disturb local circulation pattern as well as decrease in temperature due to the nighttime strong radiative cooling under the condition of snow covers.  Monsoon clouds and deep valley system caused unique surface temperature variation.

scholarly journals Tropopause height at 78° N 16° E: average seasonal variation 2007–2010

2011 ◽  
Vol 11 (1) ◽  
pp. 39-52
Author(s):  
C. M. Hall ◽  
G. Hansen ◽  
F. Sigernes ◽  
K. M. Kuyeng Ruiz
Keyword(s):  
Climate Change ◽  
Seasonal Variation ◽  
Air Temperature ◽  
High Latitude ◽  
Column Density ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Tropopause Height ◽  
Vhf Radar ◽  
Ozone Column

Abstract. We present a seasonal climatology of tropopause altitude for 78° N 16° E derived from observations 2007–2010 by the SOUSY VHF radar on Svalbard. The spring minimum occurs one month later than that of surface air temperature and instead coincides with the maximum in ozone column density. This confirms similar studies based on radiosonde measurements in the arctic and demonstrates downward control by the stratosphere. If one is to exploit the potential of tropopause height as a metric for climate change at high latitude and elsewhere, it is imperative to observe and understand the processes which establish the tropopause – an understanding to which this study contributes.

scholarly journals Tropopause height at 78° N 16° E: average seasonal variation 2007–2010

2011 ◽  
Vol 11 (11) ◽  
pp. 5485-5490 ◽  
Author(s):  
C. M. Hall ◽  
G. Hansen ◽  
F. Sigernes ◽  
K. M. Kuyeng Ruiz
Keyword(s):  
Climate Change ◽  
Seasonal Variation ◽  
Air Temperature ◽  
High Latitude ◽  
Column Density ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Tropopause Height ◽  
Vhf Radar ◽  
Ozone Column

Abstract. We present a seasonal climatology of tropopause altitude for 78° N 16° E derived from observations 2007–2010 by the SOUSY VHF radar on Svalbard. The spring minimum occurs one month later than that of surface air temperature and instead coincides with the maximum in ozone column density. This confirms similar studies based on radiosonde measurements in the arctic and demonstrates downward control by the stratosphere. If one is to exploit the potential of tropopause height as a metric for climate change at high latitude and elsewhere, it is imperative to observe and understand the processes which establish the tropopause – an understanding to which this study contributes.

scholarly journals A Climatological Study of the Nocturnal Boundary Layer over a Complex-Terrain Station

2012 ◽  
Vol 51 (4) ◽  
pp. 813-825 ◽  
Author(s):  
M. Shravan Kumar ◽  
V. K. Anandan ◽  
T. Narayana Rao ◽  
P. Narasimha Reddy
Keyword(s):  
Boundary Layer ◽  
Seasonal Variation ◽  
Monsoon Season ◽  
Inversion Layer ◽  
Nocturnal Boundary Layer ◽  
Local Circulation ◽  
Sodar Data ◽  
Doppler Sodar

AbstractTwo years of Doppler sodar measurements are used to study the time–height structure of the nocturnal boundary layer (NBL), its seasonal variation, and the characteristics of different types of NBL. A total of 220 clear-sky nights during which the inversion layer is clearly visible on a sodar echogram are examined. The NBL depth estimated with sodar data using a wind maxima criterion matches reasonably well with radiosonde-based NBL depth estimates. The NBL exhibits clear seasonal variation with greater depths during the monsoon season. Shallow NBLs are generally observed in winter. The evolution of NBL height shows two distinctly different patterns (called type 1 and type 2), particularly in the second half of the night. Type 1 NBL depth is nearly constant and the wind speed in this type is generally weak and steady throughout the night, while type 2 is characterized by moderate to strong winds with considerable variations in NBL height. The local circulation generated by the complex topography is clearly seen in type 1 throughout the night, whereas it is seen only in the first half of the night in type 2. Type 1 NBLs seem to be more prevalent over Gadanki, India, with nearly 61% of total nights showing type 1 characteristics. Furthermore, type 1 NBL shows large seasonal variability with the majority of type 1 cases in winter. The type 2 cases are mostly observed in monsoon (~60%) followed by summer (39%). The surface meteorological parameters during type 1 and type 2 cases are examined. Differences between type 1 and type 2 NBL patterns are discussed in relation to the surface forcing.

scholarly journals Urban-Induced Changes on Local Circulation in Complex Terrain: Central Mexico Basin

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 904
Author(s):  
Lourdes P. Aquino-Martínez ◽  
Arturo I. Quintanar ◽  
Carlos A. Ochoa-Moya ◽  
Erika Danaé López-Espinoza ◽  
David K. Adams ◽  
...  
Keyword(s):  
Large Scale ◽  
Meridional Circulation ◽  
Circulation Pattern ◽  
Heat Fluxes ◽  
Local Circulation ◽  
Pressure System ◽  
Near Surface ◽  
Zonal Circulation ◽  
Downslope Wind ◽  
Mexico Basin

Land use land cover (LULC) significantly impacts local circulation in the Mexico Basin, particularly wind field circulations such as gap winds, convergence lines, and thermally induced upslope/downslope wind. A case study with a high-pressure system over the Mexico Basin isolates the influence of large-scale synoptic forcing. Numerical simulations reveal a wind system composed of meridional circulation and a zonal component. Thermal pressure gradients between the Mexico basin and its colder surroundings create near-surface convergence lines as part of the meridional circulation. Experiments show that the intensity and organization of meridional circulations and downslope winds increase when LULC changes from natural and cultivated land to urban. Zonal circulation exhibits a typical circulation pattern with the upslope flow and descending motion in the middle of the basin. Large values of moist static energy are near the surface where air parcels pick up energy from the surface either as fluxes of enthalpy or latent heat. Surface heat fluxes and stored energy in the ground are drivers of local circulation, which is more evident in zonal circulation patterns.

scholarly journals Modulation of summer monsoon sub-seasonal surface air temperature over India by soil moisture-temperature coupling

MAUSAM ◽  
2021 ◽  
Vol 67 (1) ◽  
pp. 53-66
Author(s):  
M. V. S. RAMARAO ◽  
J. SANJAY ◽  
R. KRISHNAN
Keyword(s):  
Soil Moisture ◽  
Air Temperature ◽  
Summer Monsoon ◽  
Climate Models ◽  
Monsoon Season ◽  
Surface Air Temperature ◽  
Monsoon Precipitation ◽  
Summer Monsoon Season ◽  
Weather And Climate ◽  
Dry Soil

The influence of soil moisture on the sub-seasonal warmer surface air temperature anomalies during drier soil conditions associated with break spells in the Indian summer monsoon precipitation is explored using observations.  The multi-model analysis of land surface states and fluxes available from the Second Global Soil Wetness Project (GSWP-2) are found useful in understanding the mechanism for this soil moisture-temperature coupling on sub-seasonal timescales. The analysis uses a soil moisture-temperature coupling diagnostic computed based on linear correlations of daily fields. It is shown that the summer surface air temperature variations are linked to intraseasonal variations of the Indian monsoon precipitation, which control the land-climate coupling by modulating the soil moisture variations. Strong coupling mainly occurs during dry soil states within the summer monsoon season over the transition zones between wet and dry climates of central to north-west India. In contrast, the coupling is weak for constantly wet and energy-limited evaporative regimes over eastern India during the entire summer monsoon season. This observational based analysis provided a better understanding of the linkages between the sub-seasonal dry soil states and warm conditions during the Indian summer monsoon season. A proper representation of these aspects of land-atmosphere interactions in weather and climate models used for sub-seasonal and seasonal monsoon forecasting could be critical for several applications, in particular agriculture. The soil moisture-temperature coupling diagnostic used in this study will be a useful metric for evaluating the performance of weather and climate models.

Characteristics of Deep Cloud Systems under Weak and Strong Synoptic Forcing during the Indian Summer Monsoon Season

2019 ◽  
Vol 147 (10) ◽  
pp. 3741-3758 ◽  
Author(s):  
Jayesh Phadtare ◽  
G. S. Bhat
Keyword(s):  
Monsoon Season ◽  
Propagation Speed ◽  
Maximum Size ◽  
Gradient Field ◽  
Synoptic Scale ◽  
Pressure System ◽  
Cloud Systems ◽  
Convective Systems ◽  
The North ◽  
Synoptic Forcing

Abstract Synoptic-scale weather systems are often responsible for initiating mesoscale convective systems (MCSs). Here, we explore how synoptic forcing influences MCS characteristics, such as the maximum size, lifespan, cloud-top height, propagation speed, and triggering over the Indian region. We used 30-min interval infrared (IR) data of the Indian Kalpana-1 geostationary satellite. Cloud systems (CSs) in this data are identified and tracked using an object tracking algorithm. ERA-Interim 850-hPa vorticity is taken as a proxy for the synoptic forcing. The probability of CSs being larger, longer lived, and deeper is more in the presence of a synoptic-scale vorticity field; however, the influence of synoptic forcing is not evident on the westward propagation of CSs over land. There exists a linear relationship between maximum size, lifespan, and average cloud-top height of CSs regardless of the nature of synoptic forcing. Formation of CSs peaks around 1500 LST over land, which is independent of synoptic forcing. Over the north Bay of Bengal, CSs formation is predominantly nocturnal when synoptic forcing is strong, whereas, 0300 and 1200 LST are the preferred times when synoptic forcing is weak. Long-lived CSs are preferentially triggered in the western flank of the 850-hPa vorticity gradient field of a monsoon low pressure system. Once triggered, CSs propagate westward and ahead of the synoptic system and dissipate around midnight. Formation of new CSs on the next day occurs in the afternoon hours in the wake of previous day’s CSs and where vorticity gradient is also present. Formation and westward propagations of CSs on successive days move the synoptic envelope westward.

scholarly journals Variability of Indian summer monsoon: Relationship with surface air temperature anomalies over northern hemisphere

MAUSAM ◽  
2022 ◽  
Vol 44 (2) ◽  
pp. 191-198
Author(s):  
R. K. VERMA
Keyword(s):  
Northern Hemisphere ◽  
Air Temperature ◽  
Summer Monsoon ◽  
Monsoon Rainfall ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Surface Air Temperature ◽  
Time Lags ◽  
Temperature Anomalies ◽  
Air Temperature Anomalies

Thirty year (1950-79) time series of Monsoon Index (MI) is correlated with the gridded surface air temperature data over northern hemisphere land at various time lags of months (i.e., months preceding concurrent and succeeding to the monsoon season) to identify tele-connections of monsoon with the northern hemisphere surface air temperature anomalies. .   Out of three key regions identified which show statistically significant relationship of monsoon rainfall, two regions are in the higher latitudinal belt of 40oN- 70oN over North America and Eurasia which show positive correlations with temperatures during northern winter particularly during  January and February. The third region is located over northwest India and adjoining Pakistan, where the maximum positive correlation is observed to occur during the pre-li1onsoon months of April and May. These relationships suggest that cooler northern hemisphere during the preceding seasons of winter/spring over certain key regions are generally associated with below normal summer monsoon rainfall over India and vice-versa which could be useful predictors for long-range forecasting of monsoon.   There are two large regions in the northern tropics, namely, Asian and African monsoons whose temperatures reveal strong negative correlations with monsoon rainfall during the seasons concurrent and subsequent to the summer monsoon season. However, persistence of this relationship for longer period of about two seasons after the monsoon, suggests the dominant influence of  ENSO (El. Nino-Southern Oscillation) on tropical climate.  

scholarly journals 2019–2020 Australia Fire and Its Relationship to Hydroclimatological and Vegetation Variabilities

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3067
Author(s):  
Mohammad Reza Ehsani ◽  
Jorge Arevalo ◽  
Christoforus Bayu Risanto ◽  
Mostafa Javadian ◽  
Charles John Devine ◽  
...  
Keyword(s):  
High Pressure ◽  
Air Temperature ◽  
Vegetation Indices ◽  
Surface Air Temperature ◽  
Evaporative Demand ◽  
Pressure System ◽  
Near Surface ◽  
High Pressure System ◽  
Southeast Australia ◽  
The Relationship

Wildfire is a major concern worldwide and particularly in Australia. The 2019–2020 wildfires in Australia became historically significant as they were widespread and extremely severe. Linking climate and vegetation settings to wildfires can provide insightful information for wildfire prediction, and help better understand wildfires behavior in the future. The goal of this research was to examine the relationship between the recent wildfires, various hydroclimatological variables, and satellite-retrieved vegetation indices. The analyses performed here show the uniqueness of the 2019–2020 wildfires. The near-surface air temperature from December 2019 to February 2020 was about 1 °C higher than the 20-year mean, which increased the evaporative demand. The lack of precipitation before the wildfires, due to an enhanced high-pressure system over southeast Australia, prevented the soil from having enough moisture to supply the demand, and set the stage for a large amount of dry fuel that highly favored the spread of the fires.

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