Influence of radiative forcing factors on ground-air temperature coupling during the last millennium: implications for borehole climatology

Abstract. Past climate variations may be known from reconstruction methods that use proxy data as predictors. Among them, borehole reconstructions is a well established technique to recover the long term past surface air temperature (SAT) evolution. It is based on the assumption that SAT changes are strongly coupled to ground surface temperature (GST) changes and transferred to the subsurface by thermal conduction. We evaluate the SAT-GST coupling during the last millennium (LM) using simulations from the Community Earth System Model LM Ensemble (CESM-LME). The validity of such premise is explored by analyzing the structure of the SAT-GST covariance during the LM and also by investigating the evolution of the long term SAT-GST relationship. The multiple and single-forcing simulations in the CESM-LME are used to analyze the SAT-GST relationship within different regions and spatial scales and derive the influence of the different forcing factors on producing feedbacks mechanisms that alter the energy balance at the surface. The results indicate that SAT-GST coupling is strong at global and above multi-decadal time scales in the CESM-LME however a relative small variation in the long term SAT-GST relationship is also represented. Although at global scale such variation does not impact significantly the SAT-GST coupling, at local to regional scales this relationship experiences considerable long term changes mostly after the end of the 19th century. Land use land cover (LULC) changes are the main driver for decoupling SAT and GST locally and regionally since they modify the land surface properties such as albedo, surface roughness and hydrology, and thus the energy fluxes at the surface. Snow cover feedbacks due to the influence of other external forcing are also important for corrupting the long term SAT-GST coupling. Our findings suggest that such local and regional SAT-GST decoupling processes may represent a source of bias for SAT reconstructions from borehole measurement since the thermal signature imprinted in the subsurface over the affected regions is not fully representative of the long term SAT variations.

Download Full-text

Influence of radiative forcing factors on ground–air temperature coupling during the last millennium: implications for borehole climatology

Climate of the Past ◽

10.5194/cp-14-1583-2018 ◽

2018 ◽

Vol 14 (11) ◽

pp. 1583-1606 ◽

Cited By ~ 7

Author(s):

Camilo Melo-Aguilar ◽

J. Fidel González-Rouco ◽

Elena García-Bustamante ◽

Jorge Navarro-Montesinos ◽

Norman Steinert

Keyword(s):

Air Temperature ◽

Land Surface ◽

Radiative Forcing ◽

Spatial Scales ◽

Ground Surface ◽

Surface Air Temperature ◽

Small Variation ◽

Last Millennium ◽

Reconstruction Methods

Abstract. Past climate variations may be uncovered via reconstruction methods that use proxy data as predictors. Among them, borehole reconstruction is a well-established technique to recover the long-term past surface air temperature (SAT) evolution. It is based on the assumption that SAT changes are strongly coupled to ground surface temperature (GST) changes and transferred to the subsurface by thermal conduction. We evaluate the SAT–GST coupling during the last millennium (LM) using simulations from the Community Earth System Model LM Ensemble (CESM-LME). The validity of such a premise is explored by analyzing the structure of the SAT–GST covariance during the LM and also by investigating the evolution of the long-term SAT–GST relationship. The multiple and single-forcing simulations in the CESM-LME are used to analyze the SAT–GST relationship within different regions and spatial scales and to derive the influence of the different forcing factors on producing feedback mechanisms that alter the energy balance at the surface. The results indicate that SAT–GST coupling is strong at global and above multi-decadal timescales in CESM-LME, although a relatively small variation in the long-term SAT–GST relationship is also represented. However, at a global scale such variation does not significantly impact the SAT–GST coupling, at local to regional scales this relationship experiences considerable long-term changes mostly after the end of the 19th century. Land use land cover changes are the main driver for locally and regionally decoupling SAT and GST, as they modify the land surface properties such as albedo, surface roughness and hydrology, which in turn modifies the energy fluxes at the surface. Snow cover feedbacks due to the influence of other external forcing are also important for corrupting the long-term SAT–GST coupling. Our findings suggest that such local and regional SAT–GST decoupling processes may represent a source of bias for SAT reconstructions from borehole measurement, since the thermal signature imprinted in the subsurface over the affected regions is not fully representative of the long-term SAT variations.

Download Full-text

An Integrated Procedure to Determine a Reference Station Network for Evaluating and Adjusting Urban Bias in Surface Air Temperature Data

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-14-0295.1 ◽

2015 ◽

Vol 54 (6) ◽

pp. 1248-1266 ◽

Cited By ~ 28

Author(s):

Guoyu Ren ◽

Jiao Li ◽

Yuyu Ren ◽

Ziying Chu ◽

Aiying Zhang ◽

...

Keyword(s):

Climate Change ◽

Air Temperature ◽

Historical Data ◽

Spatial Scales ◽

Mainland China ◽

Surface Air Temperature ◽

Reference Station ◽

Reference Network ◽

Station Network

AbstractTrends in surface air temperature (SAT) are a critical indicator for climate change at varied spatial scales. Because of urbanization effects, however, the current SAT records of many urban stations can hardly meet the demands of the studies. Evaluation and adjustment of the urbanization effects on the SAT trends are needed, which requires an objective selection of reference (rural) stations. Based on the station history information from all meteorological stations with long-term records in mainland China, an integrated procedure for determining the reference SAT stations has been developed and is applied in forming a network of reference SAT stations. Historical data from the network are used to assess the urbanization effects on the long-term SAT trends of the stations of the national Reference Climate Network and Basic Meteorological Network (RCN+BMN or national stations), which had been used most frequently in studies of regional climate change throughout the country. This paper describes in detail the integrated procedure and the assessment results of urbanization effects on the SAT trends of the national stations applying the data from the reference station network determined using the procedure. The results showed a highly significant urbanization effect of 0.074°C (10 yr)−1 and urbanization contribution of 24.9% for the national stations of mainland China during the time period 1961–2004, which compared well to results that were reported in previous studies by the authors using the predecessor of the present reference network and the reference stations selected but when applying other methods. The authors are thus confident that the SAT data from the updated China reference station network as reported in this paper best represented the baseline SAT trends nationwide and could be used for evaluating and adjusting the urban biases in the historical data series of the SAT from different observational networks.

Download Full-text

Analysis of methodological and physical bias on borehole temperature reconstructions from a pseudo-proxy approach.

10.5194/egusphere-egu2020-20483 ◽

2020 ◽

Author(s):

Camilo Melo Aguilar ◽

Fidel González Rouco ◽

Elena García Bustamante ◽

Norman Steinert ◽

Jorge Navarro ◽

...

Keyword(s):

Grid Point ◽

Ground Surface ◽

Temporal Distribution ◽

Surface Air Temperature ◽

Internal Variability ◽

Last Millennium ◽

Subsurface Temperature ◽

Borehole Logs ◽

Spatio Temporal

<p>The analysis of subsurface temperature measurements from boreholes is a well established approach for reconstructing last millennium (LM) surface air temperature (SAT). It is based on the assumption that SAT variations are strongly coupled to ground surface temperature (GST) variations and transferred to the subsurface by thermal conduction. We have evaluated the long-term SAT-GST coupling over the LM using an ensemble of both full- and single-forcing simulations form the Community Earth System Model-Last Millennium Ensemble (CESM-LME). Such a premise is explored by investigating the evolution of the long-term SAT&#8211;GST relationship. The results indicate that SAT&#8211;GST coupling is strong at global and above multi-decadal timescales in CESM-LME. However, at local to regional scales this relationship experiences considerable long-term changes mostly after the end of the 19th century. Land use land cover (LULC) changes stand as the main driver for locally and regionally decoupling SAT and GST, due to the changes in the energy fluxes at the surface. Snow cover feedbacks due to the influence of GHG forcing are also important for corrupting the long-term SAT&#8211;GST coupling. These processes may represent a source of bias for SAT reconstructions from GST borehole profiles. In light of these findings, we subsequently assessed the potential effects on SAT reconstructions from the borehole method in pseudo-proxy experiments that make use of the same set of simulations from the CESM-LME. First, a heat-conduction forward model has been used to estimate subsurface temperature-anomaly profiles using simulated GST as boundary conditions. Subsequently, singular value decomposition inversion (SVD) has been applied to reconstruct LM GST variations from the simulated profiles. We implemented and ideal scenario in which it is assumed the existence of borehole logs at every model grid point. Further, this scenario considers that all boreholes are logged homogenously at the same time. In addition, we implemented a more realistic approach in which the real-world spatio-temporal distribution of the global borehole network is considered. Results show that the SVD inversion is able to retrieve the long-term GST variations over the LM when an appropriated coverture of borehole logs is available. However, due to the limited spatio-temporal distribution of the actual borehole network, there is a lost in the accuracy to retrieve the simulated GST 20th century trends, with the temporal logging of the BTPs as the main sampling issue. Furthermore, in the surrogate reality of the CESM-LME the SAT-GST decoupling, due to the influence of LULC and GHG forcings, leads to a slightly underestimation of SAT warming during the industrial period across the CESM-LME. The level of impact is, however, highly depended on the realization of internal variability.</p>

Download Full-text

Repeated temperature logs from the sites of the Czech, Slovenian and Portuguese borehole climate stations

Climate of the Past Discussions ◽

10.5194/cpd-3-631-2007 ◽

2007 ◽

Vol 3 (2) ◽

pp. 631-653

Author(s):

J. Šafanda ◽

D. Rajver ◽

A. Correia ◽

P. Dědeček

Keyword(s):

Air Temperature ◽

Ground Surface ◽

Surface Air Temperature ◽

Deep Borehole ◽

Site Specific ◽

Forcing Function ◽

Recent Warming ◽

History Of ◽

Specific Factors

Abstract. Two borehole climate stations were established in Slovenia and Portugal within a joint Czech-Slovenian-Portuguese project in the years 2003–2005. They completed the older Czech station, which has been operating since the year 1994. We report here on the repeated temperature logs carried out within 6 boreholes at the sites of the stations and their surroundings within a time span of 8–20 years (1985–2005). The repeated logs revealed subsurface warming in all the boreholes amounting to 0.2–0.6°C below the depth of the annual run at 20 m. The depth of the Czech borehole (140 m) and the Portuguese borehole (180 m) was sufficient enough for a reconstruction of the ground surface temperature (GST) history of the last 150–200 years and their comparison with the surface air temperature (SAT) series measured in Prague (since 1771) and Lisbon (1856), respectively. The reconstructed histories reproduce reasonably well the amplitude of the recent warming, 1–1.5°C above the long-term mean. The depth of all four Slovenian boreholes, 100 m, did not allow the inversion, but it was possible to apply it to a deep borehole 5 km apart from the Slovenian station. The obtained GST history was compared with SAT series from Ljubljana (since 1851). Alternatively, a compatibility of the observed temporal changes of subsurface temperature with surface air temperature series measured in Prague, Ljubljana and Lisbon was checked by comparing differences of the repeated logs with the synthetic ones. These were calculated by using the SAT series as a forcing function at a surface of transient geothermal models of the borehole sites. A degree of agreement varies from very well to rather poor, probably depending on unaccounted site specific factors, which are to be specified by a long-term temperature monitoring at the established stations.

Download Full-text

Development of Global Hourly 0.5° Land Surface Air Temperature Datasets

Journal of Climate ◽

10.1175/jcli-d-12-00682.1 ◽

2013 ◽

Vol 26 (19) ◽

pp. 7676-7691 ◽

Cited By ~ 41

Author(s):

Aihui Wang ◽

Xubin Zeng

Keyword(s):

Air Temperature ◽

Diurnal Cycle ◽

Land Surface ◽

Surface Air Temperature ◽

Linear Interpolation ◽

Research Unit ◽

Climate Studies ◽

Modern Era

Abstract Land surface air temperature (SAT) is one of the most important variables in weather and climate studies, and its diurnal cycle is also needed for a variety of applications. Global long-term hourly SAT observational data, however, do not exist. While such hourly products could be obtained from global reanalyses, they are found to be unrealistic in representing the SAT diurnal cycle. Global hourly 0.5° SAT datasets are developed here based on four reanalysis products [Modern-Era Retrospective Analysis for Research and Applications (MERRA for 1979–2009), 40-yr ECMWF Re-Analysis (ERA-40 for 1958–2001), ECMWF Interim Re-Analysis (ERA-Interim for 1979–2009), and NCEP–NCAR reanalysis for 1948–2009)] and the Climate Research Unit Time Series version 3.10 (CRU TS3.10) for 1948–2009. The three-step adjustments include the spatial downscaling to 0.5° grid cells, the temporal interpolation from 6-hourly (in ERA-40 and NCEP–NCAR reanalysis) to hourly using the MERRA hourly SAT climatology for each day (and the linear interpolation from 3-hourly in ERA-Interim to hourly), and the bias correction in both monthly-mean maximum (Tmax) and minimum (Tmin) SAT using the CRU data. The final products have exactly the same monthly Tmax and Tmin as the CRU data, and perform well in comparison with in situ hourly measurements over six sites and with a regional daily SAT dataset over Europe. They agree with each other much better than the original reanalyses, and the spurious SAT jumps of reanalyses over some regions are also substantially eliminated. One of the uncertainties in the final products can be quantified by their differences in the true monthly mean (using 24-hourly values) and the monthly averaged diurnal cycle.

Download Full-text

Simulation of Global Land Surface Conditions from 1948 to 2004. Part I: Forcing Data and Evaluations

Journal of Hydrometeorology ◽

10.1175/jhm540.1 ◽

2006 ◽

Vol 7 (5) ◽

pp. 953-975 ◽

Cited By ~ 323

Author(s):

Taotao Qian ◽

Aiguo Dai ◽

Kevin E. Trenberth ◽

Keith W. Oleson

Keyword(s):

Soil Moisture ◽

Air Temperature ◽

Land Surface ◽

Surface Air Temperature ◽

Reanalysis Data ◽

Freshwater Discharge ◽

Land Surface Models ◽

Surface Conditions ◽

Surface Models

Abstract Because of a lack of observations, historical simulations of land surface conditions using land surface models are needed for studying variability and changes in the continental water cycle and for providing initial conditions for seasonal climate predictions. Atmospheric forcing datasets are also needed for land surface model development. The quality of atmospheric forcing data greatly affects the ability of land surface models to realistically simulate land surface conditions. Here a carefully constructed global forcing dataset for 1948–2004 with 3-hourly and T62 (∼1.875°) resolution is described, and historical simulations using the latest version of the Community Land Model version 3.0 (CLM3) are evaluated using available observations of streamflow, continental freshwater discharge, surface runoff, and soil moisture. The forcing dataset was derived by combining observation-based analyses of monthly precipitation and surface air temperature with intramonthly variations from the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis, which is shown to have spurious trends and biases in surface temperature and precipitation. Surface downward solar radiation from the reanalysis was first adjusted for variations and trends using monthly station records of cloud cover anomaly and then for mean biases using satellite observations during recent decades. Surface specific humidity from the reanalysis was adjusted using the adjusted surface air temperature and reanalysis relative humidity. Surface wind speed and air pressure were interpolated directly from the 6-hourly reanalysis data. Sensitivity experiments show that the precipitation adjustment (to the reanalysis data) leads to the largest improvement, while the temperature and radiation adjustments have only small effects. When forced by this dataset, the CLM3 reproduces many aspects of the long-term mean, annual cycle, interannual and decadal variations, and trends of streamflow for many large rivers (e.g., the Orinoco, Changjiang, Mississippi, etc.), although substantial biases exist. The simulated long-term-mean freshwater discharge into the global and individual oceans is comparable to 921 river-based observational estimates. Observed soil moisture variations over Illinois and parts of Eurasia are generally simulated well, with the dominant influence coming from precipitation. The results suggest that the CLM3 simulations are useful for climate change analysis. It is also shown that unrealistically low intensity and high frequency of precipitation, as in most model-simulated precipitation or observed time-averaged fields, result in too much evaporation and too little runoff, which leads to lower than observed river flows. This problem can be reduced by adjusting the precipitation rates using observed-precipitation frequency maps.

Download Full-text

Regularities of soil temperature changes during the period with snow cover in modern climatic conditions of the Eurasian Subarctic

Journal of the Belarusian State University. Geography and Geology ◽

10.33581/2521-6740-2021-1-13-22 ◽

2021 ◽

pp. 13-22

Author(s):

Lev M. Kitaev

Keyword(s):

Standard Deviation ◽

Soil Temperature ◽

Snow Cover ◽

Air Temperature ◽

Land Surface ◽

Environmental Changes ◽

Surface Air Temperature ◽

Climatic Conditions ◽

Winter Period

The influence of snow cover on the dynamics of soil temperature in the modern climatic conditions of the Eurasian Subarctic was investigated through a quantitative assessment of the features of the seasonal and long-term variation of parameters. Seasonal and long-term values of soil temperature for stable snow period decrease from west to east: a decrease of snow thickness and air temperature from west to east of Eurasia leads to a weakening of the heat-insulating properties of the snow cover with a significant decrease in regional air temperatures. With the emergence of a stable snow cover, the soil temperature seasonal and long-term standard deviation sharply decreases compared to the autumn and spring periods. With the appearance of snow cover, the soil temperature standard deviation drops sharply compared to the autumn and spring periods. An exception is the northeast of Siberia: here, a relatively small thickness of snow determines a noticeable dependence of the course of soil temperature on the dynamics of surface air temperature. There are no significant long-term trends in soil temperature due to its low variability during winter period. Analysis of the course of the studied characteristics anomalies showed an insignificant and non-systematic number of their coincidences. Currently, we have not found similar research results for large regions. The revealed patterns can be used in the analysis of the results of monitoring the state of the land surface, in the development of remote sensing algorithms, in the refinement of predictive scenarios of environmental changes.

Download Full-text

Evaluation and Comparison of Noah and Pleim–Xiu Land Surface Models in MM5 Using GÖTE2001 Data: Spatial and Temporal Variations in Near-Surface Air Temperature

Journal of Applied Meteorology and Climatology ◽

10.1175/jam2561.1 ◽

2007 ◽

Vol 46 (10) ◽

pp. 1587-1605 ◽

Cited By ~ 37

Author(s):

J-F. Miao ◽

D. Chen ◽

K. Borne

Keyword(s):

Soil Moisture ◽

Air Temperature ◽

Land Surface ◽

Model Performance ◽

Surface Air Temperature ◽

Near Surface ◽

Surface Models ◽

Urban Heat ◽

Soil Moisture Initialization ◽

Evident Difference

Abstract In this study, the performance of two advanced land surface models (LSMs; Noah LSM and Pleim–Xiu LSM) coupled with the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5), version 3.7.2, in simulating the near-surface air temperature in the greater Göteborg area in Sweden is evaluated and compared using the GÖTE2001 field campaign data. Further, the effects of different planetary boundary layer schemes [Eta and Medium-Range Forecast (MRF) PBLs] for Noah LSM and soil moisture initialization approaches for Pleim–Xiu LSM are investigated. The investigation focuses on the evaluation and comparison of diurnal cycle intensity and maximum and minimum temperatures, as well as the urban heat island during the daytime and nighttime under the clear-sky and cloudy/rainy weather conditions for different experimental schemes. The results indicate that 1) there is an evident difference between Noah LSM and Pleim–Xiu LSM in simulating the near-surface air temperature, especially in the modeled urban heat island; 2) there is no evident difference in the model performance between the Eta PBL and MRF PBL coupled with the Noah LSM; and 3) soil moisture initialization is of crucial importance for model performance in the Pleim–Xiu LSM. In addition, owing to the recent release of MM5, version 3.7.3, some experiments done with version 3.7.2 were repeated to reveal the effects of the modifications in the Noah LSM and Pleim–Xiu LSM. The modification to longwave radiation parameterizations in Noah LSM significantly improves model performance while the adjustment of emissivity, one of the vegetation properties, affects Pleim–Xiu LSM performance to a larger extent. The study suggests that improvements both in Noah LSM physics and in Pleim–Xiu LSM initialization of soil moisture and parameterization of vegetation properties are important.

Download Full-text