Assimilation of Pseudo-Tree-Ring-Width observations into an Atmospheric General Circulation Model

Abstract. We investigate the assimilation of Tree-Ring-Width (TRW) chronologies into an atmospheric global climate model using Ensemble Kalman Filter (EnKF) techniques and a process-based tree-growth forward model as observation operator. Our results, within a perfect-model experiment setting, indicate that the non-linear response of tree-growth to surface temperature and soil moisture does deteriorate the operation of the time-averaged (EnKF) methodology. Moreover, this skill loss appeared significantly sensitive to the structure of growth rate function, used to represent the Principle of Limiting Factors (PLF)s within the forward model. On the other hand, it was observed that the error reduction achieved by assimilating a particular pseudo-TRW chronology is modulated by the strength of the yearly internal variability of the model at the chronology site. This result might help the dendrochronology community to optimize their sampling efforts. In our experiments, the ''online'' (with cycling) paleao Data Assimilation (DA) approach did not outperform the ''offline'' (no-cycling) one, despite its considerable additional implementation complexity.

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Assimilation of pseudo-tree-ring-width observations into an atmospheric general circulation model

Climate of the Past ◽

10.5194/cp-13-545-2017 ◽

2017 ◽

Vol 13 (5) ◽

pp. 545-557 ◽

Cited By ~ 9

Author(s):

Walter Acevedo ◽

Bijan Fallah ◽

Sebastian Reich ◽

Ulrich Cubasch

Keyword(s):

Tree Ring ◽

Tree Growth ◽

General Circulation ◽

Climate Model ◽

Global Climate Model ◽

Ring Width ◽

Circulation Model ◽

Forward Model ◽

Limiting Factors ◽

Tree Ring Width

Abstract. Paleoclimate data assimilation (DA) is a promising technique to systematically combine the information from climate model simulations and proxy records. Here, we investigate the assimilation of tree-ring-width (TRW) chronologies into an atmospheric global climate model using ensemble Kalman filter (EnKF) techniques and a process-based tree-growth forward model as an observation operator. Our results, within a perfect-model experiment setting, indicate that the "online DA" approach did not outperform the "off-line" one, despite its considerable additional implementation complexity. On the other hand, it was observed that the nonlinear response of tree growth to surface temperature and soil moisture does deteriorate the operation of the time-averaged EnKF methodology. Moreover, for the first time we show that this skill loss appears significantly sensitive to the structure of the growth rate function, used to represent the principle of limiting factors (PLF) within the forward model. In general, our experiments showed that the error reduction achieved by assimilating pseudo-TRW chronologies is modulated by the magnitude of the yearly internal variability in the model. This result might help the dendrochronology community to optimize their sampling efforts.

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Tree growth across the Nepal Himalaya during the last four centuries

Progress in Physical Geography Earth and Environment ◽

10.1177/0309133317714247 ◽

2017 ◽

Vol 41 (4) ◽

pp. 478-495 ◽

Cited By ~ 15

Author(s):

UK Thapa ◽

S St. George ◽

DK Kharal ◽

NP Gaire

Keyword(s):

Tree Ring ◽

Tree Growth ◽

Environmental Changes ◽

Ring Width ◽

High Elevation ◽

Forest Growth ◽

Tree Ring Width ◽

Early 19Th Century ◽

Tree Ring Data ◽

Instrumental Records

The climate of Nepal has changed rapidly over the recent decades, but most instrumental records of weather and hydrology only extend back to the 1980s. Tree rings can provide a longer perspective on recent environmental changes, and since the early 2000s, a new round of field initiatives by international researchers and Nepali scientists have more than doubled the size of the country’s tree-ring network. In this paper, we present a comprehensive analysis of the current tree-ring width network for Nepal, and use this network to estimate changes in forest growth nation-wide during the last four centuries. Ring-width chronologies in Nepal have been developed from 11 tree species, and half of the records span at least 290 years. The Nepal tree-ring width network provides a robust estimate of annual forest growth over roughly the last four centuries, but prior to this point, our mean ring-width composite fluctuates wildly due to low sample replication. Over the last four centuries, two major events are prominent in the all-Nepal composite: (i) a prolonged and widespread growth suppression during the early 1800s; and (ii) heightened growth during the most recent decade. The early 19th century decline in tree growth coincides with two major Indonesian eruptions, and suggests that short-term disturbances related to climate extremes can exert a lasting influence on the vigor of Nepal’s forests. Growth increases since AD 2000 are mainly apparent in high-elevation fir, which may be a consequence of the observed trend towards warmer temperatures, particularly during winter. This synthesis effort should be useful to establish baselines for tree-ring data in Nepal and provide a broader context to evaluate the sensitivity or behavior of this proxy in the central Himalayas.

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Composite Analysis of Winter Cyclones in a GCM: Influence on Climatological Humidity

Journal of Climate ◽

10.1175/jcli3690.1 ◽

2006 ◽

Vol 19 (9) ◽

pp. 1652-1672 ◽

Cited By ~ 70

Author(s):

Mike Bauer ◽

Anthony D. Del Genio

Keyword(s):

Water Vapor ◽

General Circulation ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Circulation Model ◽

Cloud Properties ◽

Frontal Zones ◽

Goddard Institute ◽

Ageostrophic Circulation

Abstract The role of midlatitude baroclinic cyclones in maintaining the extratropical winter distribution of water vapor in an operational global climate model is investigated. A cyclone identification and tracking algorithm is used to compare the frequency of occurrence, propagation characteristics, and composite structure of 10 winters of storms in the Goddard Institute for Space Studies general circulation model (GCM) and in two reanalysis products. Cyclones are the major dynamical source of water vapor over the extratropical oceans in the reanalyses. The GCM produces fewer, generally weaker, and slower-moving cyclones than the reanalyses and is especially deficient in storms associated with secondary cyclogenesis. Composite fields show that GCM cyclones are shallower and drier aloft than those in the reanalyses and that their vertical structure is less tilted in the frontal region because of the GCM’s weaker ageostrophic circulation. This is consistent with the GCM’s underprediction of midlatitude cirrus. The GCM deficiencies do not appear to be primarily due to parameterization errors; the model is too dry despite producing less storm precipitation than is present in the reanalyses and in an experimental satellite precipitation dataset, and the weakness and shallow structure of GCM cyclones is already present at storm onset. These shortcomings may be common to most climate GCMs that do not resolve the mesoscale structure of frontal zones, and this may account for some universal problems in climate GCM midlatitude cloud properties.

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Erratum to: An efficient forward model of the climate controls on interannual variation in tree-ring width

Climate Dynamics ◽

10.1007/s00382-011-1062-9 ◽

2011 ◽

Vol 36 (11-12) ◽

pp. 2441-2445 ◽

Cited By ~ 4

Author(s):

Susan E. Tolwinski-Ward ◽

Michael N. Evans ◽

Malcolm K. Hughes ◽

Kevin J. Anchukaitis

Keyword(s):

Tree Ring ◽

Interannual Variation ◽

Ring Width ◽

Forward Model ◽

Tree Ring Width ◽

Climate Controls

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Development of tree-ring width chronologies and tree-growth response to climate in the mountains surrounding the Issyk-Kul Lake, Central Asia

Dendrochronologia ◽

10.1016/j.dendro.2014.03.002 ◽

2014 ◽

Vol 32 (3) ◽

pp. 230-236 ◽

Cited By ~ 14

Author(s):

Tongwen Zhang ◽

Yujiang Yuan ◽

Qing He ◽

Wenshou Wei ◽

Mamatkanov Diushen ◽

...

Keyword(s):

Central Asia ◽

Tree Ring ◽

Tree Growth ◽

Growth Response ◽

Ring Width ◽

Tree Ring Width

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Modelling the impacts of climate change on tropospheric ozone over three centuries

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-6805-2011 ◽

2011 ◽

Vol 11 (2) ◽

pp. 6805-6843 ◽

Cited By ~ 13

Author(s):

G. B. Hedegaard ◽

A. Gross ◽

J. H. Christensen ◽

W. May ◽

H. Skov ◽

...

Keyword(s):

Climate Change ◽

Ozone Concentration ◽

General Circulation ◽

Climate Model ◽

Transport Model ◽

Global Climate ◽

Global Climate Model ◽

Circulation Model ◽

Ocean General Circulation Model ◽

The Arctic

Abstract. The ozone chemistry over three centuries has been simulated based on climate prediction from a global climate model and constant anthropogenic emissions in order to separate out the effects on air pollution from climate change. Four decades in different centuries has been simulated using the chemistry version of the atmospheric long-range transport model; the Danish Eulerian Hemispheric Model (DEHM) forced with meteorology predicted by the ECHAM5/MPI-OM coupled Atmosphere-Ocean General Circulation Model. The largest changes in both meteorology, ozone and its precursors is found in the 21st century, however, also significant changes are found in the 22nd century. At surface level the ozone concentration is predicted to increase due to climate change in the areas where substantial amounts of ozone precursors are emitted. Elsewhere a significant decrease is predicted at the surface. In the free troposphere a general increase is found in the entire Northern Hemisphere except in the tropics, where the ozone concentration is decreasing. In the Arctic the ozone concentration will increase in the entire air column, which most likely is due to changes in transport. The change in temperature, humidity and the naturally emitted Volatile Organic Compounds (VOCs) are governing with respect to changes in ozone both in the past, present and future century.

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On the ‘Divergence Problem’ in the Alatau Mountains, Central Asia: A Study of the Responses of Schrenk Spruce Tree-Ring Width to Climate under the Recent Warming and Wetting Trend

Atmosphere ◽

10.3390/atmos10080473 ◽

2019 ◽

Vol 10 (8) ◽

pp. 473 ◽

Cited By ~ 3

Author(s):

Zhang ◽

Jiang ◽

Bagila ◽

Ainur ◽

...

Keyword(s):

Central Asia ◽

Tree Ring ◽

Tree Growth ◽

Tree Species ◽

Climatic Factors ◽

Ring Width ◽

Tree Ring Width ◽

Recent Warming ◽

Divergence Problem ◽

The Stability

The divergence problem, which manifests as an unstable response relationship between tree-ring growth and climatic factors under the background of global warming, poses a challenge to both the traditional theory of dendroclimatology and the reliability of climatic reconstructions based on tree-ring data. Although Schrenk spruce, as the dominant tree species in the Tianshan Mountains, is frequently applied in the dendrochronological studies, the understanding of the divergence problem of this tree species is still limited. This study conducted correlation analysis between climatic factors and tree-ring width chronologies from 51 living and healthy specimens of Schrenk spruce at sites of high and low elevation in the Alatau Mountains to determine the stability of the response. The results revealed that the tree-ring width of the spruce specimens was correlated positively with precipitation and correlated negatively with temperature. Although the variations of the two tree-ring chronologies were similar, the radial growth of the spruce at the low elevation was found more sensitive to climatic factors. Furthermore, the sensitivity of tree growth to climate demonstrated an obvious increase after an abrupt change of climate under the background of the recent warming and wetting trend. Increased drought stress, calculated based on climatic data, was regarded as the main reason for this phenomenon. The results supply the gap of the stability of climatic response of tree growth in Central Asia to some extent.

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The Tropical Atmospheric El Niño Signal in Satellite Precipitation Data and a Global Climate Model

Journal of Climate ◽

10.1175/jcli4208.1 ◽

2007 ◽

Vol 20 (14) ◽

pp. 3580-3601 ◽

Cited By ~ 14

Author(s):

Yonghua Chen ◽

Anthony D. Del Genio ◽

Junye Chen

Keyword(s):

El Niño ◽

General Circulation ◽

Climate Model ◽

El Nino ◽

Global Climate ◽

Global Climate Model ◽

Circulation Model ◽

Western Indian Ocean ◽

Correlation Technique ◽

Atmospheric Response

Abstract Aspects of the tropical atmospheric response to El Niño related to the global energy and water cycle are examined using satellite retrievals from the Tropical Rainfall Measuring Mission and the Advanced Microwave Scanning Radiometer-E and simulations from the Goddard Institute for Space Studies (GISS) general circulation model (GCM). The El Niño signal is extracted from climate fields using a linear cross-correlation technique that captures local and remote in-phase and lagged responses. Passive microwave and radar precipitation anomalies for the 1997/98 and 2002/03 El Niños and the intervening La Niña are highly correlated, but anomalies in stratiform–convective rainfall partitioning in the two datasets are not. The GISS GCM produces too much rainfall in general over ocean and too little over land. Its atmospheric response to El Niño is weaker and decays a season too early. Underestimated stratiform rainfall fraction (SRF) and convective downdraft mass flux in the GISS GCM and excessive shallow convective and low stratiform cloud result in latent heating that peaks at lower altitudes than inferred from the data. The GISS GCM also underestimates the column water vapor content throughout the Tropics, which causes it to overestimate outgoing longwave radiation. The response of both quantities to interannual Hadley circulation anomalies is too weak. The GISS GCM’s Walker circulation also exhibits a weak remote response to El Niño, especially over the Maritime Continent and western Indian Ocean. This appears to be a consequence of weak static stability due to the model’s lack of upper-level stratiform anvil heating, excessive low-level heating, and excessive dissipation due to cumulus momentum mixing. Our results suggest that parameterizations of mesoscale updrafts, convective downdrafts, and cumulus-scale pressure gradient effects on momentum transport are keys to a reasonable GISS GCM simulation of tropical interannual variability.

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Mid-Pliocene global climate simulation with MRI-CGCM2.3: set-up and initial results of PlioMIP Experiments 1 and 2

Geoscientific Model Development ◽

10.5194/gmd-5-793-2012 ◽

2012 ◽

Vol 5 (3) ◽

pp. 793-808 ◽

Cited By ~ 26

Author(s):

Y. Kamae ◽

H. Ueda

Keyword(s):

General Circulation ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Climate Simulation ◽

Polar Regions ◽

The North ◽

Set Up

Abstract. The mid-Pliocene (3.3 to 3.0 million yr ago), a globally warm period before the Quaternary, is recently attracting attention as a new target for paleoclimate modelling and data-model synthesis. This paper reports set-ups and results of experiments proposed in Pliocene Model Intercomparison Project (PlioMIP) using a global climate model, MRI-CGCM2.3. We conducted pre-industrial and mid-Pliocene runs by using the coupled atmosphere-ocean general circulation model (AOGCM) and its atmospheric component (AGCM) for the PlioMIP Experiments 2 and 1, respectively. In addition, we conducted two types of integrations in AOGCM simulation, with and without flux adjustments on sea surface. General characteristics of differences in the simulated mid-Pliocene climate relative to the pre-industrial in the three integrations are compared. In addition, patterns of predicted mid-Pliocene biomes resulting from the three climate simulations are compared in this study. Generally, difference of simulated surface climate between AGCM and AOGCM is larger than that between the two AOGCM runs, with and without flux adjustments. The simulated climate shows different pattern between AGCM and AOGCM particularly over low latitude oceans, subtropical land regions and high latitude oceans. The AOGCM simulations do not reproduce wetter environment in the subtropics relative to the present-day, which is suggested by terrestrial proxy data. The differences between the two types of AOGCM runs are small over the land, but evident over the ocean particularly in the North Atlantic and polar regions.

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Optimal Spectral Nudging for Global Dynamic Downscaling

Monthly Weather Review ◽

10.1175/mwr-d-16-0036.1 ◽

2017 ◽

Vol 145 (3) ◽

pp. 909-927 ◽

Cited By ~ 13

Author(s):

Martina Schubert-Frisius ◽

Frauke Feser ◽

Hans von Storch ◽

Sebastian Rast

Keyword(s):

General Circulation ◽

Climate Model ◽

Global Climate ◽

Spatial Scales ◽

Global Climate Model ◽

Circulation Model ◽

Prognostic Variables ◽

Reanalysis Dataset ◽

Spectral Nudging ◽

High Dependency

This study analyzes a method of constructing a homogeneous, high-resolution global atmospheric hindcast. The method is the spectral nudging technique, which was applied to a state-of-the-art general circulation model (ECHAM6, T255L95). Large spatial scales of the global climate model prognostic variables were spectrally nudged toward a reanalysis dataset (NCEP-1, T62L28) for the past few decades. The main idea is the addition of dynamically consistent regional weather details to the coarse-grid NCEP-1 reanalysis. A large number of sensitivity experiments was performed, using different nudging e-folding times, vertical profiles, wavenumbers, and variables. Comparisons with observations and several reanalyses showed a high dependency on the variations of the nudging configuration. At the global scale, the accordance is very high for extratropical regions and lower in the tropics. A wavenumber truncation of 30, a relatively short e-folding time of 50 min, and a plateau-shaped nudging profile applied only to divergence and vorticity generally yielded the best results. This is one of the first global spectral nudging hindcast studies and the first applying an altitude-dependent profile to selected prognostic variables. The method can be applied to reconstructing the history of extreme events such as intense storms within the context of ongoing climate change.

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