Intercomparison of Precipitation Estimates over the Southern Ocean from Atmospheric Reanalyses

2020 ◽  
Vol 33 (24) ◽  
pp. 10627-10651
Author(s):  
Linette N. Boisvert ◽  
Melinda A. Webster ◽  
Alek A. Petty ◽  
Thorsten Markus ◽  
Richard I. Cullather ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Spatial Patterns ◽  
Harsh Environment ◽  
Polar Regions ◽  
Direct Observations ◽  
Large Spread ◽  
Precipitation Estimates ◽  
Ice Mass Balance ◽  
Annual Means ◽  
Background Models

AbstractPrecipitation is a major component of the hydrologic cycle and plays a significant role in the sea ice mass balance in the polar regions. Over the Southern Ocean, precipitation is particularly uncertain due to the lack of direct observations in this remote and harsh environment. Here we demonstrate that precipitation estimates from eight global reanalyses produce similar spatial patterns between 2000 and 2010, although their annual means vary by about 250 mm yr−1 (or 26% of the median values) and there is little similarity in their representation of interannual variability. ERA-Interim produces the smallest and CFSR produces the largest amount of precipitation overall. Rainfall and snowfall are partitioned in five reanalyses; snowfall suffers from the same issues as the total precipitation comparison, with ERA-Interim producing about 128 mm less snowfall and JRA-55 about 103 mm more rainfall compared to the other reanalyses. When compared to CloudSat-derived snowfall, these five reanalyses indicate similar spatial patterns, but differ in their magnitude. All reanalyses indicate precipitation on nearly every day of the year, with spurious values occurring on an average of about 60 days yr−1, resulting in an accumulation of about 4.5 mm yr−1. While similarities in spatial patterns among the reanalyses suggest a convergence, the large spread in magnitudes points to issues with the background models in adequately reproducing precipitation rates, and the differences in the model physics employed. Further improvements to model physics are required to achieve confidence in precipitation rate, as well as the phase and frequency of precipitation in these products.

Remote sensing in Antarctica and the Southern Ocean: applications and developments

1990 ◽  
Vol 2 (2) ◽  
pp. 105-121 ◽  
Author(s):  
James A. Maslanik ◽  
Roger G. Barry
Keyword(s):  
Remote Sensing ◽  
Southern Ocean ◽  
Polar Regions ◽  
Ice Shelf ◽  
Direct Observations ◽  
Sensing Applications ◽  
Ocean Atmosphere ◽  
Remote Sensing Applications ◽  
New Instruments ◽  
Existing Data

Remote sensing provides the means to study features and processes that are not easily accessible or amenable to direct observations. The polar regions, and Antarctica in particular, offer a variety of examples where the ability to observe from afar is necessary or highly desirable. In particular, studies of ice shelf processes, changes in the sea-ice cover, and ice-ocean-atmosphere investigations must rely in large part on measurements from aircraft and satellites. The polar regions present a unique set of problems that complicate applications and limit the usefulness of certain sensors; new instruments planned for launch in the 1990s will help resolve many of these difficulties. Examples of remote sensing applications for the study of the continent, drifting ice, ocean, and atmosphere demonstrate ways that existing data as well as new observations can be used to aid polar research.

scholarly journals Blowing snow detection from ground-based ceilometers: application to East Antarctica

2017 ◽  
Vol 11 (6) ◽  
pp. 2755-2772 ◽  
Author(s):  
Alexandra Gossart ◽  
Niels Souverijns ◽  
Irina V. Gorodetskaya ◽  
Stef Lhermitte ◽  
Jan T. M. Lenaerts ◽  
...  
Keyword(s):  
Wind Speed ◽  
Numerical Models ◽  
East Antarctica ◽  
Added Value ◽  
Polar Regions ◽  
Blowing Snow ◽  
Surface Mass ◽  
Direct Observations ◽  
Synoptic Conditions ◽  
Fresh Snow

Abstract. Blowing snow impacts Antarctic ice sheet surface mass balance by snow redistribution and sublimation. However, numerical models poorly represent blowing snow processes, while direct observations are limited in space and time. Satellite retrieval of blowing snow is hindered by clouds and only the strongest events are considered. Here, we develop a blowing snow detection (BSD) algorithm for ground-based remote-sensing ceilometers in polar regions and apply it to ceilometers at Neumayer III and Princess Elisabeth (PE) stations, East Antarctica. The algorithm is able to detect (heavy) blowing snow layers reaching 30 m height. Results show that 78 % of the detected events are in agreement with visual observations at Neumayer III station. The BSD algorithm detects heavy blowing snow 36 % of the time at Neumayer (2011–2015) and 13 % at PE station (2010–2016). Blowing snow occurrence peaks during the austral winter and shows around 5 % interannual variability. The BSD algorithm is capable of detecting blowing snow both lifted from the ground and occurring during precipitation, which is an added value since results indicate that 92 % of the blowing snow is during synoptic events, often combined with precipitation. Analysis of atmospheric meteorological variables shows that blowing snow occurrence strongly depends on fresh snow availability in addition to wind speed. This finding challenges the commonly used parametrizations, where the threshold for snow particles to be lifted is a function of wind speed only. Blowing snow occurs predominantly during storms and overcast conditions, shortly after precipitation events, and can reach up to 1300 m a. g. l.  in the case of heavy mixed events (precipitation and blowing snow together). These results suggest that synoptic conditions play an important role in generating blowing snow events and that fresh snow availability should be considered in determining the blowing snow onset.

scholarly journals The impacts of climate change on marine mammals: early signs of significant problems

Oryx ◽  
2007 ◽  
Vol 41 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Mark P. Simmonds ◽  
Stephen J. Isaac
Keyword(s):  
Climate Change ◽  
Marine Mammal ◽  
Marine Mammals ◽  
Delphinapterus Leucas ◽  
Polar Regions ◽  
Baleen Whale ◽  
Direct Observations ◽  
Management Plans ◽  
Conservation Plans ◽  
Impacts Of Climate Change

Climate change is now known to be affecting the oceans. It is widely anticipated that impacts on marine mammals will be mediated primarily via changes in prey distribution and abundance and that the more mobile (or otherwise adaptable) species may be able to respond to this to some extent. However, the extent of this adaptability is largely unknown. Meanwhile, within the last few years direct observations have been made of several marine mammal populations that illustrate reactions to climate change. These observations indicate that certain species and populations may be especially vulnerable, including those with a limited habitat range, such as the vaquita Phocoena sinus, or those for which sea ice provides an important part of their habitat, such as narwhals Monodon monoceros, bowhead Balaena mysticetus and beluga Delphinapterus leucas whales and polar bears Ursus maritimus. Similarly, there are concerns about those species that migrate to feeding grounds in polar regions because of rapidly changing conditions there, and this includes many baleen whale populations. This review highlights the need to take projected impacts into account in future conservation and management plans, including species assessments. How this should be done in an adequately precautionary manner offers a significant challenge to those involved in such processes, although it is possible to identify at this time at least some species and populations that may be regarded as especially vulnerable. Marine ecosystems modellers and marine mammal experts will need to work together to make such assessments and conservation plans as robust as possible.

scholarly journals Revisiting extreme precipitation amounts over southern South America and implications for the Patagonian Icefields

2020 ◽  
Vol 24 (4) ◽  
pp. 2003-2016 ◽  
Author(s):  
Tobias Sauter
Keyword(s):  
Sea Level ◽  
Environmental Changes ◽  
Net Primary Production ◽  
Precipitation Amount ◽  
Moisture Flux ◽  
Polar Regions ◽  
Surface Mass ◽  
Precipitation Estimates ◽  
Modelling Studies ◽  
New Perspective

Abstract. Patagonia is thought to be one of the wettest regions on Earth, although available regional precipitation estimates vary considerably. This uncertainty complicates understanding and quantifying the observed environmental changes, such as glacier recession, biodiversity decline in fjord ecosystems and enhanced net primary production. The Patagonian Icefields, for example, are one of the largest contributors to sea-level rise outside the polar regions, and robust hydroclimatic projections are needed to understand and quantify current and future mass changes. The reported projections of precipitation from numerical modelling studies tend to overestimate those from in situ determinations, and the plausibility of these numbers has never been carefully scrutinized, despite the significance of this topic to our understanding of observed environmental changes. Here I use simple physical arguments and a linear model to test the plausibility of the current precipitation estimates and its impact on the Patagonian Icefields. The results show that environmental conditions required to sustain a mean precipitation amount exceeding 6.09±0.64 m yr−1 are untenable according to the regional moisture flux. The revised precipitation values imply a significant reduction in the surface mass balance of the Patagonian Icefields compared to previously reported values. This yields a new perspective on the response of Patagonia's glaciers to climate change and their sea-level contribution and might also help reduce uncertainties in the change of other precipitation-driven environmental phenomena.

scholarly journals A global survey of aerosol-liquid water cloud overlap based on four years of CALIPSO-CALIOP data

2011 ◽  
Vol 11 (3) ◽  
pp. 1143-1154 ◽  
Author(s):  
A. Devasthale ◽  
M. A. Thomas
Keyword(s):  
Liquid Water ◽  
Radiative Forcing ◽  
Feature Detection ◽  
Quality Criteria ◽  
Polar Regions ◽  
Hemispheric Differences ◽  
Aerosol Cloud ◽  
Water Cloud ◽  
Annual Means ◽  
Absorbing Aerosols

Abstract. Simulating the radiative impacts of aerosols located above liquid water clouds presents a significant challenge. In particular, absorbing aerosols, such as smoke, may have significant impact in such situations and even change the sign of net radiative forcing. It is not possible to reliably obtain information on such overlap events from existing passive satellite sensors. However, the CALIOP instrument onboard NASA's CALIPSO satellite allows us to examine these events with unprecedented accuracy. Using four years of collocated CALIPSO 5 km Aerosol and Cloud Layer Version 3 Products (June 2006–May 2010), we quantify, for the first time, the characteristics of overlapping aerosol and water cloud layers globally. We investigate seasonal variability in these characteristics over six latitude bands to understand the hemispheric differences when all aerosol types are included in the analysis (the AAO case). We also investigate frequency of smoke aerosol-cloud overlap (the SAO case). Globally, the frequency is highest during the JJA months in the AAO case, while for the SAO case, it is highest in the SON months. The seasonal mean overlap frequency can regionally exceed 20% in the AAO case and 10% in the SAO case. In about 5–10% cases the vertical distance between aerosol and cloud layers is less than 100 m, while about in 45–60% cases it less than a kilometer in the annual means for different latitudinal bands. In about 70–80% cases, aerosol layers are less than a kilometer thick, while in about 18–22% cases they are 1–2 km thick. The frequency of aerosol layers 2–3 km thick is about 4–5% in the tropical belts during overlap events. Over the regions where high aerosol loadings are present, the overlap frequency can be up to 50% higher when quality criteria on aerosol/cloud feature detection are relaxed. Over the polar regions, more than 50% of the overlapping aerosol layers have optical thickness less than 0.02, but the contribution from the relatively optically thicker aerosol layers increases towards the equatorial regions in both hemispheres. The results suggest that the frequency of occurrence of overlap events is far from being negligible globally.

scholarly journals Development of 1961-1990 monthly surface climatology of India and patterns of differences of some meteorological parameters with respect to the 1951-1980 climatology

MAUSAM ◽  
2022 ◽  
Vol 63 (3) ◽  
pp. 377-390
Author(s):  
A.K. JASWAL ◽  
S.R. BHAMBAK ◽  
M.K. GUJAR ◽  
S.H. MOHITE ◽  
S. ANANTHARAMAN ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Spatial Patterns ◽  
Large Scale ◽  
India Meteorological Department ◽  
Cloud Amount ◽  
Climatic Conditions ◽  
Maximum Temperature ◽  
Annual Means ◽  
Rainy Days

Climate normals are used to describe the average climatic conditions of a particular place and are computed by National Meteorological Services of all countries. The World Meteorological Organization (WMO) recommends that all countries prepare climate normals for the 30-year periods ending in 1930, 1960, 1990 and so on, for which the WMO World Climate Normals are published. Recently, Climatological Normals for the period 1961-1990 have been prepared by India Meteorological Department (IMD) which will change the baseline of comparison from 1951-1980. In this paper, preparation of the 30-year Climatological Normals of India for the period 1961 to 1990 and spatial patterns of differences of annual means of temperatures, relative humidity, clouds, rainfall and wind speed from the previous normals (1951-1980) are documented.The changes from earlier climatological normals indicate increase in annual means of maximum temperature, relative humidity and decrease in annual means of minimum temperature, cloud amount, rainfall, rainy days and wind speed over large parts of the country during 1961-1990. The spatial patterns of changes in dry bulb temperatures and relative humidity are complementary over most parts of the country. Compared with 1951-1980 climatology, there are large scale decreases in annual mean rainfall, rainy days and wind speed over most parts of the country during 1961-1990. The decrease in wind speed may be partly due to changes in exposure conditions of observatories due to urbanization.

Causes and consequences of Southern Ocean change: the IPCC SROCC assessment

2020 ◽  
Author(s):  
Michael Meredith ◽  
Martin Sommerkorn ◽  
Sandra Cassotta ◽  
Chris Derksen ◽  
Alexey Ekaykin ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Sea Level ◽  
Ocean Circulation ◽  
Global Climate ◽  
Ice Sheets ◽  
The Arctic ◽  
Polar Regions ◽  
Ice Shelves

<p>Climate change in the polar regions exerts a profound influence both locally and over all of our planet.  Physical and ecosystem changes influence societies and economies, via factors that include food provision, transport and access to non-renewable resources.  Sea level, global climate and potentially mid-latitude weather are influenced by the changing polar regions, through coupled feedback processes, sea ice changes and the melting of snow and land-based ice sheets and glaciers.</p><p>Reflecting this importance, the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) features a chapter highlighting past, ongoing and future change in the polar regions, the impacts of these changes, and the possible options for response.  The role of the polar oceans, both in determining the changes and impacts in the polar regions and in structuring the global influence, is an important component of this chapter.</p><p>With emphasis on the Southern Ocean and through comparison with the Arctic, this talk will outline key findings from the polar regions chapter of SROCC. It will synthesise the latest information on the rates, patterns and causes of changes in sea ice, ocean circulation and properties. It will assess cryospheric driving of ocean change from ice sheets, ice shelves and glaciers, and the role of the oceans in determining the past and future evolutions of polar land-based ice. The implications of these changes for climate, ecosystems, sea level and the global system will be outlined.</p>

The Temperature of the Upper Atmosphere*

1946 ◽  
Vol 27 (6) ◽  
pp. 331-342 ◽  
Author(s):  
R. Penndorf
Keyword(s):  
Sound Propagation ◽  
Thermal Structure ◽  
Upper Atmosphere ◽  
Atmospheric Tides ◽  
Polar Regions ◽  
Radiation Density ◽  
Direct Observations

Summary The thermal structure of the stratosphere and ionosphere is more elaborate than has heretofore been assumed. No appreciable rise in temperature up to 30 km is indicated from direct observations. A temperature of + 50°C at a height of 50 km is supported by the results on anomalous sound propagation, and of research on ozone and meteors, as well as by the theory of atmospheric tides. At heights around 50 to 80 km, the temperature again falls to −70°C, and afterwards rises again to somewhere between + 60°C and + 160°C at a height of 100 km. At heights around 200 to 250 km, the temperature is probably between + 160°C and + 560°C. In the polar regions at 100 km, the temperature is about −40°C, showing the marked difference due to latitude. A new definition for the concept of temperature in the upper atmosphere is given, since allowance must be made for radiation density.

scholarly journals Warm Middle Jurassic–Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean

2012 ◽  
Vol 8 (1) ◽  
pp. 215-226 ◽  
Author(s):  
H. C. Jenkyns ◽  
L. Schouten-Huibers ◽  
S. Schouten ◽  
J. S. Sinninghe Damsté
Keyword(s):  
Southern Ocean ◽  
Early Cretaceous ◽  
Middle Jurassic ◽  
Warming Trend ◽  
Upper Jurassic ◽  
Climatic Conditions ◽  
Sea Surface ◽  
Polar Regions ◽  
Sea Surface Temperatures ◽  
Surface Temperatures

Abstract. Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the Middle Jurassic indicates that relatively warm sea-surface conditions (26–30 °C) existed from this interval (∼160 Ma) to the Early Cretaceous (∼115 Ma) in the Southern Ocean, with a general warming trend through the Late Jurassic followed by a general cooling trend through the Early Cretaceous. The lowest sea-surface temperatures are recorded from around the Callovian–Oxfordian boundary, an interval identified in Europe as relatively cool, but do not fall below 25 °C. The early Aptian Oceanic Anoxic Event, identified on the basis of published biostratigraphy, total organic carbon and carbon-isotope stratigraphy, records an interval with the lowest, albeit fluctuating Early Cretaceous palaeotemperatures (∼26 °C), recalling similar phenomena recorded from Europe and the tropical Pacific Ocean. Extant belemnite δ18O data, assuming an isotopic composition of waters inhabited by these fossils of −1‰ SMOW, give palaeotemperatures throughout the Upper Jurassic–Lower Cretaceous interval that are consistently lower by ∼14 °C than does TEX86 and the molluscs likely record conditions below the thermocline. The long-term, warm climatic conditions indicated by the TEX86 data would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the Mesozoic Era.

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