scholarly journals A Long-term synoptic-scale climate study over Mariepskop, Mpumalanga, South Africa

2012 ◽  
Vol 22 (2) ◽  
pp. 2-6
Author(s):  
I. Pretorius ◽  
H. Rautenbach
Keyword(s):  
Global Warming ◽  
Surface Temperature ◽  
Wind Direction ◽  
Mountain Range ◽  
Linear Temperature ◽  
Near Surface ◽  
National Centre ◽  
Synoptic Wind ◽  
June July

Mariepskop forms part of the northernmost edge of the Drakensberg Mountain range and is known for its complex topography associated with meso-scale atmospheric circulation, and therefore its numerous climatic zones. The mountain hosts a high biodiversity. The peak of Mariepskop lies at approximately 1900m Above Mean Sea Level (AMSL), which is higher than the surrounding escarpment to the east. Its foothills also extend well into the Lowveld at about 700 m AMSL. Mariepskop is therefore ideal for studying airflow exchange between the industrial Highveld and the Lowveld with its diversity of natural resources. It is also ideal for detecting global warming signals on altitudinal gradients extending from the Lowveld to altitudes above the Highveld escarpment. In this study long-term National Centre for Atmospheric Research / National Centre for Environmental Prediction (NCAR/NCEP) wind data at two atmospheric pressure levels (850 and 700 hPa), as well as near-surface temperature data, were obtained for the Mariepskop region for the summer (December-January-February: DJF (1981-2011 )) and winter (June-July-August: JJA (1980-2012)) seasons. The data was used to study synoptic wind flow across the mountain in the upper (700 hPa) and lower (800 hPa) atmosphere, as well as near-surface temperature gradients. During the summer season, east-south-easterly and south-easterly winds were found to be the most prominent. These winds are commonly associated with both continental and ridging anticyclonic conditions. During winter, the predominant wind direction at 850 hPa is south-easterly, which is also due to the influence of ridging anticyclones, while at 700 hPa the dominant winter wind direction becomes west-south-west, which is due to the more frequent eastward passing of cyclonic frontal systems across the Highveld towards the Lowveld. Long-term near-surface temperatures exhibit a weak increasing linear temperature trend for both seasons, which might be due to global warming.

scholarly journals Recent changes (2013-2017) in scyphomedusan fauna in the Boka Kotorska Bay, Montenegro (Southeast Adriatic)

2019 ◽  
Vol 60 (1) ◽  
pp. 25-39
Author(s):  
Ivana Violić ◽  
Davor Lučić ◽  
Ivona Milić Beran ◽  
Vesna Mačić ◽  
Branka Pestorić ◽  
...  
Keyword(s):  
Time Series ◽  
Global Warming ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Water Column ◽  
Sea Surface ◽  
Long Term Trends ◽  
Sst Anomalies ◽  
Chrysaora Hysoscella

A semi- quantitative time series (2013-2017) was used to present the recent events of scyphomedusae appearance and abundance in the Boka Kotorska Bay, Montenegro, Southeast Adriatic. Six meroplanktonic species were recorded: Aurelia spp, Chrysaora hysoscella, Cotylorhiza tuberculata ̧ Discomedusa lobata, Drymonema dalmatinum and Rhizostoma pulmo. Among them, C. hysoscella and D. lobata dominated in the water column during winter and spring, forming dense aggregations in March and May, and February to May, respectively. Our description of the D. lobata blooms are actually the first known records of blooms for this species. C. tuberculata was observed in the Bay principally in August and September. The bloom was occurred only in 2017, being the first information of C. tuberculata mass appearance in this area. We hypothesized that global warming phenomena could trigger the observed changes, and in this respect, long-term trends of sea surface temperature (SST) fluctuations were analysed. The scyphomedusae blooms coincided with high positive SST anomalies, noted in the last seven years for this area. To better understand the mechanisms underlying changes in their phenology and abundance, detailed studies on benthic stages in the Bay are essential.

scholarly journals Observational evidence of temperature trends at two levels in the surface layer

2016 ◽  
Vol 16 (2) ◽  
pp. 827-841 ◽  
Author(s):  
X. Lin ◽  
R. A. Pielke Sr. ◽  
R. Mahmood ◽  
C. A. Fiebrich ◽  
R. Aiken
Keyword(s):  
Surface Layer ◽  
Surface Temperature ◽  
Current Knowledge ◽  
Observational Evidence ◽  
Lapse Rate ◽  
High Quality ◽  
Near Surface ◽  
Temperature Trends ◽  
Screen Level

Abstract. Long-term surface air temperatures at 1.5 m screen level over land are used in calculating a global average surface temperature trend. This global trend is used by the IPCC and others to monitor, assess, and describe global warming or warming hiatus. Current knowledge of near-surface temperature trends with respect to height, however, is limited and inadequately understood because surface temperature observations at different heights in the surface layer of the world are rare especially from a high-quality and long-term climate monitoring network. Here we use high-quality two-height Oklahoma Mesonet observations, synchronized in time, fixed in height, and situated in relatively flat terrain, to assess temperature trends and differentiating temperature trends with respect to heights (i.e., near-surface lapse rate trend) over the period 1997 to 2013. We show that the near-surface lapse rate has significantly decreased with a trend of −0.18 ± 0.03 °C (10 m)−1 per decade indicating that the 9 m height temperatures increased faster than temperatures at the 1.5 m screen level and/or conditions at the 1.5 m height cooled faster than at the 9 m height. However, neither of the two individual height temperature trends by themselves were statistically significant. The magnitude of lapse rate trend is greatest under lighter winds at night. Nighttime lapse rate trends were significantly more negative than daytime lapse rate trends and the average lapse rate trend was three times more negative under calm conditions than under windy conditions. Our results provide the first observational evidence of near-surface temperature changes with respect to height that could enhance the assessment of climate model predictions.

scholarly journals On the changes in the sea surface temperature in the benguela upwelling region. Part 2: the long-term tendencies

2019 ◽  
pp. 29-39 ◽  
Author(s):  
A. B. Polonsky ◽  
A. N. Serebrennikov
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Wind Field ◽  
Surface Wind ◽  
Field Structure ◽  
Sea Surface ◽  
Near Surface ◽  
Tangential Wind ◽  
Benguela Upwelling

The paper examines the issue on the long-term trends in the sea surface temperature (SST) in the Benguela upwelling zone and their causes using the daily SST satellite data for 1985–2017’s and the daily near-surface wind for 1988–2017”s. It is shown that in the Benguela upwelling region, there is a significant intensification of driving winds in the last 20 yrs. This is accompanied by a decrease of the thermal upwelling index (taking into account the sign of the index or an increase of its absolute values) in the southern part of the Benguela upwelling, but practically does not influence this indicator in its northern part. The likely reason for this difference is the change in the wind field structure, as a result of which there are opposite trends in the magnitude of the vorticity of the tangential wind stress in different parts of the Benguela upwelling. In the southern part of the Benguela upwelling, both the Ekman’s upwelling and the vertical velocities due to the vorticity of the driving wind intensify, while in the northern part the corresponding trends have the opposite signs. This leads to a partial compensation of these two effects in the northern part of the Benguela upwelling. The reason for the change in the wind field structure is the displacement of the center of the Subtropical High to the south-east and the concomitant reversal of the near-surface wind vector in the coastal zone.

Advances in the HadCRUT5 record of global near-surface temperatures since 1850

2021 ◽  
Author(s):  
Colin Morice ◽  
John Kennedy ◽  
Nick Rayner ◽  
Jonathan Winn ◽  
Emma Hogan ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Measurement Errors ◽  
Global Climate ◽  
The Arctic ◽  
Data Sets ◽  
Observation Data ◽  
Data Set ◽  
Near Surface ◽  
Temperature Records

<p>The new HadCRUT5 data set combines meteorological station air temperature records with sea-surface temperature measurements in a data set of near-surface temperature anomalies from the year 1850 to present. Major developments in HadCRUT5 include: updates to underpinning observation data holdings; use of an updated assessment of the impacts of changing marine measurement methods; and adoption of a statistical gridding method to extend estimates into sparsely observed regions of the globe, such as the Arctic. The data are presented as a 200-member ensemble that spans the assessed uncertainty associated with adjustments for long-term observational biases, observing platform measurement errors and the interaction of observational sampling with gridding methods. The impacts of methodological changes in HadCRUT5 on diagnostics of the global climate will be discussed and compared to results derived from other state-of-the-art global data sets.</p>

scholarly journals Prediction of Long-Term Near-Surface Temperature Based on NA-CORDEX Output

2019 ◽  
Author(s):  
X. Y. Li ◽  
◽  
Z. Li ◽  
Q. Q. Zhang ◽  
P. X. Zhou ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Near Surface

scholarly journals Trends in Atmospheric Humidity and Temperature above Dome C, Antarctica Evaluated from Observations and Reanalyses

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 836
Author(s):  
Philippe Ricaud ◽  
Paolo Grigioni ◽  
Romain Roehrig ◽  
Pierre Durand ◽  
Dana E. Veron
Keyword(s):  
Surface Temperature ◽  
Global Climate ◽  
Microwave Radiometer ◽  
Southern Annular Mode ◽  
Warming Trend ◽  
Near Surface ◽  
Multidecadal Variability ◽  
Drying Trend ◽  
Long Term Trends

The time evolution of humidity and temperature above Dome C (Antarctica) has been investigated by considering data from (1) meteorological radiosondes (2005–2017), (2) the microwave radiometer HAMSTRAD (2012–2017), (3) four modern meteorological reanalyses (1980–2017) and (4) the southern annular mode (SAM) index (1980–2017). From these observations (2005–2017), a significant moistening trend (0.08 ± 0.06 kg m−2 dec−1) is associated with a significant warming trend (1.08 ± 0.55 K dec−1) in summer. Conversely, a significant drying trend of −0.04 ± 0.03 kg m−2 dec−1 (−0.05 ± 0.03 kg m−2 dec−1) is associated with a significant cooling trend of −2.4 ± 1.2 K dec−1 (−5.1 ± 2.0 K dec−1) in autumn (winter), with no significant trends in the spring. We demonstrate that 1) the trends identified in the radiosondes (2005–2017) are also present in the reanalyses and 2) the multidecadal variability of integrated water vapor and near-surface temperature (1980–2017) is strongly influenced by variability in the SAM index for all seasons but spring. Our study suggests that the decadal trends observed in humidity and near-surface temperature at Dome C (2005–2017) reflect the multidecadal variability of the atmosphere, and are not indicative of long-term trends that may be related to global climate change.

Physics of Changes in Synoptic Midlatitude Temperature Variability

2015 ◽  
Vol 28 (6) ◽  
pp. 2312-2331 ◽  
Author(s):  
Tapio Schneider ◽  
Tobias Bischoff ◽  
Hanna Płotka
Keyword(s):  
Global Warming ◽  
Surface Temperature ◽  
Northern Hemisphere ◽  
Potential Temperature ◽  
Temperature Variability ◽  
Temperature Gradients ◽  
Arctic Amplification ◽  
Near Surface ◽  
Temperature Variations ◽  
Temperature Variance

Abstract This paper examines the physical processes controlling how synoptic midlatitude temperature variability near the surface changes with climate. Because synoptic temperature variability is primarily generated by advection, it can be related to mean potential temperature gradients and mixing lengths near the surface. Scaling arguments show that the reduction of meridional potential temperature gradients that accompanies polar amplification of global warming leads to a reduction of the synoptic temperature variance near the surface. This is confirmed in simulations of a wide range of climates with an idealized GCM. In comprehensive climate simulations (CMIP5), Arctic amplification of global warming similarly entails a large-scale reduction of the near-surface temperature variance in Northern Hemisphere midlatitudes, especially in winter. The probability density functions of synoptic near-surface temperature variations in midlatitudes are statistically indistinguishable from Gaussian, both in reanalysis data and in a range of climates simulated with idealized and comprehensive GCMs. This indicates that changes in mean values and variances suffice to account for changes even in extreme synoptic temperature variations. Taken together, the results indicate that Arctic amplification of global warming leads to even less frequent cold outbreaks in Northern Hemisphere winter than a shift toward a warmer mean climate implies by itself.

scholarly journals Observational evidence of temperature trends at two levels in the surface layer

2015 ◽  
Vol 15 (17) ◽  
pp. 24695-24726
Author(s):  
X. Lin ◽  
R. A. Pielke Sr. ◽  
R. Mahmood ◽  
C. A. Fiebrich ◽  
R. Aiken
Keyword(s):  
Surface Layer ◽  
Surface Temperature ◽  
Current Knowledge ◽  
Observational Evidence ◽  
Lapse Rate ◽  
High Quality ◽  
Near Surface ◽  
Temperature Trends ◽  
Screen Level

Abstract. Long-term surface air temperatures at 1.5 m screen level over land are used in calculating a global average surface temperature trend. This global trend is used by the IPCC and others to monitor, assess, and describe global warming or warming hiatus. Current knowledge of near-surface temperature trends with respect to height, however, is limited and inadequately understood because surface temperature observations at different heights in the surface layer in the world are rare especially from a high-quality and long-term climate monitoring network. Here we use high-quality two-height Oklahoma Mesonet observations, synchronized in time, fixed in height, and situated in relatively flat terrain, to assess temperature trends and differentiating temperature trends with respect to heights (i.e., near-surface lapse rate trend) over the period 1997 to 2013. We show that the near-surface lapse rate has significantly decreased with a trend of −0.18 ± 0.03 °C (10 m)−1 decade−1 indicating that the 9 m height temperatures increased faster than temperatures at the 1.5 m screen level and conditions at the 1.5 m height cooled faster than at the 9 m height. However, neither of the two individual height temperature trends by themselves were statistically significant. The magnitude of lapse rate trend is greatest under lighter winds at night. Nighttime lapse rate trends were significantly more negative than daytime lapse rate trends and the average lapse rate trend was three times more negative under calm conditions than under windy conditions. Our results provide the first observational evidence of near-surface temperature changes with respect to height that could enhance the assessment of climate model predictions.

Sign in / Sign up

Export Citation Format

Share Document