Long-term changes of precipitation in Latvia

2010 ◽  
Vol 41 (3-4) ◽  
pp. 241-252 ◽  
Author(s):  
Lita Lizuma ◽  
Agrita Briede ◽  
Maris Klavins
Keyword(s):  
Extreme Precipitation ◽  
Winter Season ◽  
Cold Season ◽  
Annual Precipitation ◽  
Precipitation Pattern ◽  
Term Trend ◽  
Positive Tendency ◽  
Extreme Precipitation Events ◽  
Long Term Trend

This study investigated long-term variability and trends in Latvia's annual, seasonal, monthly and daily precipitation using data from 10 meteorological stations for the period 1925–2006 and from station Riga University for the period 1850–2006. The obtained results indicate that during the 20th century a significant increase in precipitation has occurred in the cold season while the warm period showed a decreasing tendency. The annual precipitation totals showed a slight decrease, at half of the studied stations, due to opposite tendencies in cold season and warm season. The long-term trend in the annual precipitation in Riga (from 1850) was positive with large interannual and interdecadal variability. The extreme precipitation events were evaluated using a set of nine climate change indices. Of these, number of wet days, 1-day and 5-days maximum precipitation, moderate wet days and very wet days showed a well pronounced positive tendency in the cold period of the year particularly in winter. No overall long-term trend was detected in extreme precipitation in summer. As in the case of 150-year precipitation pattern, extreme precipitation exhibited cyclic fluctuations that were more pronounced than linear changes. The close correlation between North Atlantic oscillation (NAO) and extreme precipitation was found for winter season.

Understanding Precipitation Characteristics of Afghanistan at Provincial Scale

2021 ◽  
Author(s):  
Shakti Suryavanshi ◽  
Nitin Joshi ◽  
Hardeep Kumar Maurya ◽  
Divya Gupta ◽  
Keshav Kumar Sharma
Keyword(s):  
Extreme Precipitation ◽  
Asian Country ◽  
Annual Precipitation ◽  
Precipitation Pattern ◽  
Precipitation Trend ◽  
Extreme Precipitation Events ◽  
Changing Patterns ◽  
Extreme Precipitation Indices ◽  
Precipitation Indices ◽  
Precipitation Events

Abstract This study examines the pattern and trend of seasonal and annual precipitation along with extreme precipitation events in a data scare, south Asian country, Afghanistan. Seven extreme precipitation indices were considered based upon intensity, duration and frequency of precipitation events. The study revealed that precipitation pattern of Afghanistan is unevenly distributed at seasonal and yearly scales. Southern and Southwestern provinces remain significantly dry whereas, the Northern and Northeastern provinces receive comparatively higher precipitation. Spring and winter seasons bring about 80% of yearly precipitation in Afghanistan. However, a notable declining precipitation trend was observed in these two seasons. An increasing trend in precipitation was observed for the summer and autumn seasons, however; these seasons are the lean periods for precipitation. A declining annual precipitation trend was also revealed in many provinces of Afghanistan. Analysis of extreme precipitation indices reveals a general drier condition in Afghanistan. Large spatial variability was found in precipitation indices. In many provinces of Afghanistan, a significantly declining trends were observed in intensity-based (Rx1-day, RX5-day, SDII and R95p) and frequency-based (R10) precipitation indices. The duration-based precipitation indices (CDD and CWD) also infer a general drier climatic condition in Afghanistan. This study will assist the agriculture and allied sectors to take well-planned adaptive measures in dealing with the changing patterns of precipitation, and additionally, facilitating future studies for Afghanistan.

scholarly journals Analysis of 24 years of mesopause region OH rotational temperature observations at Davis, Antarctica – Part 1: long-term trends

2020 ◽  
Vol 20 (11) ◽  
pp. 6379-6394 ◽  
Author(s):  
W. John R. French ◽  
Frank J. Mulligan ◽  
Andrew R. Klekociuk
Keyword(s):  
Solar Cycle ◽  
Rotational Temperature ◽  
Winter Season ◽  
Pressure Level ◽  
Recent Analysis ◽  
Research Station ◽  
Mesopause Region ◽  
Term Trend ◽  
Long Term Trend

Abstract. The long-term trend, solar cycle response, and residual variability in 24 years of hydroxyl nightglow rotational temperatures above Davis research station, Antarctica (68∘ S, 78∘ E) are reported. Hydroxyl rotational temperatures are a layer-weighted proxy for kinetic temperatures near 87 km altitude and have been used for many decades to monitor trends in the mesopause region in response to increasing greenhouse gas emissions. Routine observations of the OH(6-2) band P-branch emission lines using a scanning spectrometer at Davis station have been made continuously over each winter season since 1995. Significant outcomes of this most recent analysis update are the following: (a) a record-low winter-average temperature of 198.3 K is obtained for 2018 (1.7 K below previous low in 2009); (b) a long-term cooling trend of -1.2±0.51 K per decade persists, coupled with a solar cycle response of 4.3±1.02 K per 100 solar flux units; and (c) we find evidence in the residual winter mean temperatures of an oscillation on a quasi-quadrennial (QQO) timescale which is investigated in detail in Part 2 of this work. Our observations and trend analyses are compared with satellite measurements from Aura/MLS version v4.2 level-2 data over the last 14 years, and we find close agreement (a best fit to temperature anomalies) with the 0.00464 hPa pressure level values. The solar cycle response (3.4±2.3 K per 100 sfu), long-term trend (-1.3±1.2 K per decade), and underlying QQO residuals in Aura/MLS are consistent with the Davis observations. Consequently, we extend the Aura/MLS trend analysis to provide a global view of solar response and long-term trend for Southern and Northern Hemisphere winter seasons at the 0.00464 hPa pressure level to compare with other observers and models.

Late Holocene Climate Changes in Eastern North America Estimated from Pollen Data

1988 ◽  
Vol 29 (3) ◽  
pp. 255-262 ◽  
Author(s):  
K. Gajewski
Keyword(s):  
Summer Temperature ◽  
Annual Precipitation ◽  
Climate Data ◽  
Term Trend ◽  
The Past ◽  
Modern Pollen ◽  
Time Control ◽  
Regression Techniques ◽  
Long Term Trend

Well-dated pollen profiles from six sites from Maine to Minnesota record vegetation changes indicative of summer temperature and annual precipitation variations over the past 2000 yr. Laminations in the sediment provide accurate time control. Multiple regression techniques were used to calculate calibration functions from a spatial network of modern pollen and climate data. When applied to the six pollen diagrams, these calibration functions yielded estimates that show a long-term trend toward lower summer temperature. Superimposed on this long-term trend are short-term fluctuations that are frequently in phase at the sites. Departures from the long-term cooling trend are positive around 1500 yr ago (indicating relative warmth) and negative between 200 and 500 yr ago (indicating relative cold). Annual precipitation showed a slight increase at several sites during the past 1000 yr relative to the previous 1000 yr.

scholarly journals Long-Term Trend Analysis of Precipitation and Extreme Events over Kosi River Basin in India

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1695
Author(s):  
Prashant K Srivastava ◽  
Rajani Kumar Pradhan ◽  
George P. Petropoulos ◽  
Varsha Pandey ◽  
Manika Gupta ◽  
...  
Keyword(s):  
River Basin ◽  
Extreme Precipitation ◽  
Trend Test ◽  
Hydrological Process ◽  
Clear Trend ◽  
Extreme Rainfall Events ◽  
Term Trend ◽  
Sen’S Slope ◽  
Long Term Trend

Analysis of spatial and temporal changes of long-term precipitation and extreme precipitation distribution at a local scale is very important for the prevention and mitigation of water-related disasters. In the present study, we have analyzed the long-term trend of 116 years (1901–2016) of precipitation and distribution of extreme precipitation index over the Kosi River Basin (KRB), which is one of the frequent flooding rivers of India, using the 0.25° × 0.25° resolution gridded precipitation datasets obtained from the Indian Meteorological Department (IMD), India. The non-parametric Mann–Kendall trend test together with Sen’s slope estimator was employed to determine the trend and the magnitude of the trend of the precipitation time series. The annual and monsoon seasons revealed decreasing trends with Sen’s slope values of −1.88 and −0.408, respectively. For the extreme indices viz. R10 and R20 days, a decreasing trend from the northeastern to the southwest part of the basin can be observed, whereas, in the case of highest one-day precipitation (RX1 day), no clear trend was found. The information provided through this study can be useful for policymakers and may play an important role in flood management, runoff, and understanding related to the hydrological process of the basin. This will contribute to a better understanding of the potential risk of changing rainfall patterns, especially the extreme rainfall events due to climatic variations.

Long-term trend analysis on total and extreme precipitation over Shasta Dam watershed

2018 ◽  
Vol 626 ◽  
pp. 244-254 ◽  
Author(s):  
Kinya Toride ◽  
Dylan L. Cawthorne ◽  
Kei Ishida ◽  
M. Levent Kavvas ◽  
Michael L. Anderson
Keyword(s):  
Trend Analysis ◽  
Extreme Precipitation ◽  
Term Trend ◽  
Long Term Trend

Changes and variability of extreme precipitation index in Colombia

2020 ◽  
Author(s):  
Juan Diego Giraldo-Osorio ◽  
David Enrique Trujillo-Osorio ◽  
Oscar Manuel Báez-Villanueva
Keyword(s):  
Extreme Precipitation ◽  
Extreme Values ◽  
Future Trend ◽  
Mean Annual Precipitation ◽  
Andean Region ◽  
Term Trend ◽  
Spatial Coverage ◽  
The Future ◽  
Long Term Trend

<p>Climate models have not achieved a consensus about the future trend of long-term average of precipitation. As well as, the future trend of extreme values (including both extreme, droughts and heavy events) has higher uncertainties, because are unusual events. The Colombian territory is permanently in risk due to precipitation climatic extremes: during El Niño years, the rain amounts are severely reduced, consequently the rivers flow and the water resource availability; nevertheless, during La Niña years, floods and landslides events are common, because the rain is excessive.</p><p>The precipitation extremes are affected due to long-term trends and the inter-annual variability represented by El Niño/La Niña cycle, then conduct this study is relevant. The selected study area is the Colombian territory. A Satellite Rainfall Estimate (SRE) was used to ensure a whole spatial coverage. The SRE has a daily temporary resolution, then it is suitable for building the selected Extreme Precipitation Indices (EPI). Statistical tests were carried out to verify the long-term change of EPI. The hydrological years were discriminated according to the ENSO, in order to perform a statistical test to probe the hypothesis that EPI, during these particular years (El Niño/La Niña), belong to probability distributions different from that distribution of EPI in “normal” years.</p><p>Mean annual precipitation in the Andean region drops in El Niño years, and it increases in La Niña years. In the Colombian Pacific basin, the number of wet days is reduced by the long-term trend, but the variable is not affected by the ENSO phenomena. However, in the Andean region and the eastern plains, El Niño has a high effect on reducing the number of wet days. Finally, extreme events are affected by both the long-term trend and the ENSO phenomena too; however, the change spatial distribution reveals a high impact on the Andean region.</p>

scholarly journals Analysis of 24 years of mesopause region OH rotational temperature observations at Davis, Antarctica – Part 1: Long-term trends

2020 ◽  
Author(s):  
W. John R. French ◽  
Frank J. Mulligan ◽  
Andrew R. Klekociuk
Keyword(s):  
Solar Cycle ◽  
Rotational Temperature ◽  
Winter Season ◽  
Recent Analysis ◽  
Research Station ◽  
Mesopause Region ◽  
Term Trend ◽  
Hemisphere Winter ◽  
Long Term Trend

Abstract. The long term trend, solar cycle response and residual variability in 24 years of hydroxyl nightglow rotational temperatures above Davis Research Station, Antarctica (68° S, 78° E) is reported. Hydroxyl rotational temperatures are a layer-weighted proxy for kinetic temperatures near 87 km altitude and have been used for many decades to monitor trends in the mesopause region in response to increasing greenhouse gas emissions. Routine observations of the OH(6–2) band P-branch emission lines using a scanning spectrometer at Davis station have been made continuously over each winter season since 1995. Significant outcomes of this most recent analysis update are (a) a record low winter-average temperature of 198.3 K is obtained for 2018 (1.7 K below previous low in 2009) (b) a long term cooling trend of 1.2 K/decade persists, coupled with a solar cycle response of 4.3 K/100 solar flux units and (c) we find evidence in the residual winter mean temperatures of an oscillation on a quasi-quadrennial (QQO) timescale which is investigated in detail in part 2 of this work. Our observations and trend analyses are compared with satellite measurements from Aura/MLS version v4.2 level 2 data over the last 14 years and we find close agreement (a best fit) with the 0.00464 hPa pressure level values. The solar cycle response, long-term trend and underlying QQO residuals are consistent with the Davis observations. Consequently, we extend the Aura/MLS trend analysis to provide a global view of solar response and long term trend for southern and northern hemisphere winter season to compare with other observers and models.

NAEP Trends: Main NAEP vs. Long-Term Trend

2010 ◽  
Author(s):  
Albert E. Beaton ◽  
James R. Chromy
Keyword(s):  
Term Trend ◽  
Long Term Trend
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