Seasonal Reconstruction of Summer Precipitation Variability and Dating of Flood Events for the Millennium Between 3250 and 2250 Years BC for the Main Region, Southern Germany

Latest drought events and their already visible damage to trees highlight the crucial need to assess the current state and resilience of forest ecosystems in southern Germany. However, commonly applied dendroclimatic approaches rarely take into account, how weather patterns affecting trees are modified by topographic conditions. For this purpose, three main tree species were studied at three low mountain ranges and three corresponding basins in the topographically complex province of Bavaria (southeast Germany). A response analysis between climate proxies and tree-ring widths was used to investigate climate-growth relationships over the past 50 years of both coniferous and deciduous tree species at each forest site. Temporal stability of tree responses to climate was compared for two 25-year periods to detect possible modifications in climate-growth correlations. A pointer year analysis was also conducted to analyze tree response to climatic extreme events. The results showed that Scots pine (Pinus sylvestris) was the most vulnerable and least drought-resistant of the investigated tree species. Although Norway spruce (Picea abies) and European beech (Fagus sylvatica) benefited from an extended growing season at high elevation sites, they showed higher drought sensitivity over the past 25 years. Beech responses were rather inhomogeneous and even differed in the optimal precipitation period. However, lower correlation coefficients for summer precipitation at the driest site may indicate the ability of beech to adapt to less summer precipitation. Nevertheless, increasing drought frequency, as predicted, poses a serious threat to all studied tree species, including even the colder and more humid sites. Hence, to more accurately estimate risk potentials under future weather conditions, we will combine dendroclimatological results with climate modelling scenarios, particularly expected future frequencies of critical weather types on the local scale.

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Representation of the Angolan low and Southern African Summer Precipitation in the CORDEX and CMIP5 models.

10.5194/egusphere-egu21-12531 ◽

2021 ◽

Author(s):

Sabina Abba-Omar ◽

Francesca Raffaele ◽

Erika Coppola ◽

Daniela Jacob ◽

Claas Teichmann ◽

...

Keyword(s):

Climate Change ◽

Regression Analysis ◽

Southern Africa ◽

Summer Precipitation ◽

Precipitation Variability ◽

Cmip5 Models ◽

Impact Of Climate Change ◽

The Future ◽

Rainfall Patterns ◽

The Impact

The impact of climate change on precipitation over Southern Africa is of particular interest due to its possible devastating societal impacts. To add to this, simulating precipitation is challenging and models tend to show strong biases over this region, especially during the Austral Summer (DJF) months. One of the reasons for this is the mis-representation of the Angolan Low (AL) and its influence on Southern Africa&#8217;s Summer precipitation in the models. Therefore, this study aims to explore and compare different models&#8217; ability to capture the AL and its link to precipitation variability as well as consider the impact climate change may have on this link. We also explore how the interaction between ENSO, another important mode of variability for precipitation, and the Angolan Low, impact precipitation, how the models simulate this and whether this could change in the future under climate change.&#160;We computed the position and strength of the AL in reanalysis data and compared these results to three different model ensembles with varying resolutions. Namely, the CORDEX-CORE ensemble (CCORE), a new phase of CORDEX simulations with higher resolutions (0.22 degrees), the lower resolution (0.44 degrees) CORDEX-phase 1 ensemble (C44) and the CMIP5 models that drive the two RCM ensembles. We also used Self Organizing Maps to group DJF yearly anomaly patterns and identify which combination of ENSO and AL strength scenarios are responsible for particularly wet or dry conditions. Regression analysis was performed to analyze the relationships between precipitation and the AL and ENSO. This analysis was repeated for near (2041-2060) and far (2080-2099) future climate and compared with the present to understand how the strength of the AL, and its connection to precipitation variability and ENSO, changes in the future.&#160;We found that, in line with previous studies, models with stronger AL tend to produce more rainfall. CCORE tends to simulate a stronger AL than C44 and therefore, higher precipitation biases. However, the regression analysis shows us that CCORE is able to capture the relationship between precipitation and the AL strength variability as well as ENSO better than the other ensembles. We found that generally dry rainfall patterns over Southern Africa are associated with a weak AL and El Nino event whereas wet rainfall patterns occur during a strong AL and La Nina year. While the models are able to capture this, they also tend to show more neutral ENSO conditions associated with these wet and dry patterns which possibly indicates less of a connection between AL strength and ENSO than seen in the observed results. Analysis of the future results indicates that the AL weakens, this is shown across all the ensembles and could be a contributing factor to some of the drying seen. These results have applications in understanding and improving model representation of precipitation over Southern Africa as well as providing some insight into the impact of climate change on precipitation and some of its associated dynamics over this region.

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Two millennia of Main region (southern Germany) hydroclimate variability

Climate of the Past ◽

10.5194/cp-15-1677-2019 ◽

2019 ◽

Vol 15 (5) ◽

pp. 1677-1690 ◽

Cited By ~ 4

Author(s):

Alexander Land ◽

Sabine Remmele ◽

Jutta Hofmann ◽

Daniel Reichle ◽

Margaret Eppli ◽

...

Keyword(s):

Transfer Function ◽

Response Analysis ◽

Limited Area ◽

Limited Region ◽

Southern Germany ◽

The Past ◽

Main River ◽

River Region ◽

The Stability ◽

Main Region

Abstract. A reconstruction of hydroclimate with an annual resolution covering millennia for a geographically limited region in continental Europe significantly improves our knowledge of past climate dynamics. With the use of an extensive collection of oak ring-width series (Quercus robur and Quercus petraea) from living trees, historic timbers and subfossil alluvial wood deposits from the Main River region in southern Germany, a regional, 2000-year long, seasonally resolved hydroclimate reconstruction for the Main region has been developed. Climate-growth response analysis has been performed with daily climate records from AD 1900 onwards. To test the stability of the developed transfer function, a bootstrapped transfer function stability test (BTFS) as well as a classical calibration/verification approach have been implemented to study climate-growth model performance. Living oak trees from the Main River region show a significant sensitivity to the precipitation sum from 26 February to 6 July (spring to midsummer) during the full (r=0.49, p<0.01, N=116) and split (r=0.58, p<0.01, N=58) calibration periods. BTFS confirmed the stability of the developed transfer function. The developed precipitation reconstruction reveals high variability on a high- to mid-frequency scale during the past two millennia. Very dry spring to midsummer seasons lasting multiple years appeared in the decades AD 500/510s, 940s, 1170s, 1390s and 1160s. At the end of the AD 330s, a persistent multi-year drought with drastically reduced rainfall (with regard to 1901–2000) could be identified, which was the driest decade over the past 2000 years in this region. In the AD 550s, 1050s, 1310s and 1480s, multi-year periods with high rainfall hit the Main region. In spring to midsummer of AD 338, precipitation was reduced by ∼38 % and in AD 357 it increased by ∼39 %. The presented hydroclimate reconstruction and its comparison to other records reveal interesting insights into the hydroclimate dynamics of the geographically limited area over the Common Era, in addition to revealing noticeable temporal differences.

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Central-West Argentina Summer Precipitation Variability and Atmospheric Teleconnections

Journal of Climate ◽

10.1175/jcli-d-11-00206.1 ◽

2012 ◽

Vol 25 (5) ◽

pp. 1657-1677 ◽

Cited By ~ 19

Author(s):

Eduardo A. Agosta ◽

Rosa H. Compagnucci

Keyword(s):

Indian Ocean ◽

Southern Oscillation ◽

Vertical Motion ◽

Summer Precipitation ◽

Western Indian Ocean ◽

Stationary Wave ◽

Precipitation Variability ◽

South Atlantic ◽

Spectral Variation ◽

The South

The interannual-to-multidecadal variability of central-west Argentina (CWA) summer (October–March) precipitation and associated tropospheric circulation are studied in the period 1900–2010. Precipitation shows significant quasi cycles with periods of about 2, 4–5, 6–8, and 16–22 yr. The quasi-bidecadal oscillation is significant from the early 1910s until the mid-1970s and is present in pressure time series over the southwestern South Atlantic. According to the lower-frequency spectral variation, a prolonged wet spell is observed from 1973 to the early 2000s. The precipitation variability shows a reversal trend since then. In that wet epoch, the regionally averaged precipitation has been increased about 24%. The lower-frequency spectral variation is attributed to the climate shift of 1976/77. From the early twentieth century until the mid-1970s, the precipitation variability is associated with barotropic quasi-stationary wave (QSW) propagation from the tropical southern Indian Ocean and the South Pacific, generating vertical motion and moisture anomalies at middle-to-subtropical latitudes east of the Andes over southern South America. The QSW propagation could be related to anomalous convection partly induced by tropical anomalous SSTs in the western Indian Ocean (WIO). It could also be linked to another midlatitude source along the storm tracks, to the east of New Zealand. After 1976/77, the precipitation variability is associated with equatorial symmetric circulation anomalies linked to El Niño–Southern Oscillation (ENSO)-like warmer conditions. Positive moisture anomalies are consistently observed at lower latitudes in association with inflation of the western flank of the South Atlantic anticyclone. Outside of this, the precipitation variability is unrelated to ENSO.

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Impact of Trans-Atlantic-Pacific Ocean Dipole–like pattern on summer precipitation variability over West Africa

Atmospheric and Oceanic Science Letters ◽

10.1080/16742834.2018.1529533 ◽

2018 ◽

Vol 11 (6) ◽

pp. 509-517 ◽

Cited By ~ 3

Author(s):

Zhao-Hui LIN ◽

DIKE Victor Nnamdi

Keyword(s):

Pacific Ocean ◽

West Africa ◽

Summer Precipitation ◽

Precipitation Variability

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Summer precipitation variability over Southeastern South America in a global warming scenario

Climate Dynamics ◽

10.1007/s00382-011-1141-y ◽

2011 ◽

Vol 38 (9-10) ◽

pp. 1867-1883 ◽

Cited By ~ 34

Author(s):

C. Junquas ◽

C. Vera ◽

L. Li ◽

H. Le Treut

Keyword(s):

Global Warming ◽

South America ◽

Summer Precipitation ◽

Precipitation Variability ◽

Warming Scenario ◽

Global Warming Scenario

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SST–North American Hydroclimate Links in AMIP Simulations of the Drought Working Group Models: A Proxy for the Idealized Drought Modeling Experiments

Journal of Climate ◽

10.1175/2010jcli3174.1 ◽

2010 ◽

Vol 23 (10) ◽

pp. 2585-2598 ◽

Cited By ~ 3

Author(s):

Alfredo Ruiz-Barradas ◽

Sumant Nigam

Keyword(s):

United States ◽

Great Plains ◽

Working Group ◽

Climate Model ◽

Linear Trend ◽

Summer Precipitation ◽

The United States ◽

Precipitation Variability ◽

Drought Severity ◽

Model Experiments

Abstract The present study assesses the potential of the U.S. Climate Variability and Predictability (CLIVAR) Drought Working Group (DWG) models in simulating interannual precipitation variability over North America, especially the Great Plains. It also provides targets for the idealized DWG model experiments investigating drought origin. The century-long Atmospheric Model Intercomparison Project (AMIP) simulations produced by version 3.5 of NCAR’s Community Atmosphere Model (CAM3.5), the Lamont-Doherty Earth Observatory’s Community Climate Model (CCM3), and NASA’s Seasonal-to-Interannual Prediction Project (NSIPP-1) atmospheric models are analyzed; CCM3 and NSIPP-1 models have 16- and 14-ensemble simulations, respectively, while CAM3.5 only has 1. The standard deviation of summer precipitation is different in AMIP simulations. The maximum over the central United States seen in observations is placed farther to the west in simulations. Over the central plains the models exhibit modest skill in simulating low-frequency precipitation variability, a Palmer drought severity index proxy. The presence of a linear trend increases correlations in the period 1950–99 when compared with those for the whole century. The SST links of the Great Plains drought index have features in common with observations over both the Pacific and Atlantic Oceans. Interestingly, summer-to-fall precipitation regressions of the warm Trend, cold Pacific, and warm Atlantic modes of annual mean SST variability (used in forcing the DWG idealized model experiments) tend to dry the southwestern, midwestern, and southeastern regions of the United States in the observations and, to a lesser extent, in the simulations. The similarity of the idealized SST-forced droughts in DWG modeling experiments with AMIP precipitation regressions of the corresponding SST principal components, evident especially in the case of the cold Pacific pattern, suggests that the routinely conducted AMIP simulations could have served as an effective proxy for the more elaborated suite of DWG modeling experiments.

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