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  • 1
    Online Resource
    Online Resource
    Predictive Skill and Predictable Patterns of the U.S. Seasonal Precipitation in CFSv2 Reforecasts of 60 Years (1958–2017)
    American Meteorological Society ; 2019
    In:  Journal of Climate Vol. 32, No. 24 ( 2019-12-15), p. 8603-8637
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 32, No. 24 ( 2019-12-15), p. 8603-8637
    Abstract: Analyzing a set of ensemble seasonal reforecasts for 1958–2017 using CFSv2, we evaluate the predictive skill of the U.S. seasonal mean precipitation and examine its sources of predictability. Our analysis is for each of the three periods of 1958–78, 1979–99, and 2000–17, corresponding to the positive phase of the Pacific decadal oscillation (PDO) during 1979–99 and negative ones before and after. The ensemble reforecasts at two-month lead reproduce the spatial distribution of winter precipitation trends throughout the 60 years and the continental-scale increase of summer precipitation since 2000. The predicted signal-to-noise (S/N) ratio also reveals greater predictability in the post-1979 period than during 1958–78. A maximized S/N ratio EOF analysis is applied to the ensemble seasonal precipitation predictions. In winter and spring, the most predictable patterns feature a north–south dipole throughout United States. The summer and fall patterns are dominated by the anomalies in central and southern United States, respectively. In verification with observations, the winter–spring patterns are more skillful. ENSO influences on these predictable patterns are most dominant in winter and spring, but other oceanic factors also play an active role during summer and fall. The multidecadal change of the U.S. precipitation predictability is attributable to the low-frequency modulation of the ENSO predictability and the influences of other major climate modes. PDO can be a dominant factor associated with enhanced prediction skill in 1979–99 and reduced skill in 1958–78. Since the 2000s, the forcing from the SST anomalies in the tropical North Atlantic with opposite sign to those in the tropical Pacific becomes a significant factor for the U.S. summer precipitation prediction.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-19-0230.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2019
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 2
    Online Resource
    Online Resource
    Predictability and prediction of Indian summer monsoon by CFSv2: implication of the initial shock effect
    Springer Science and Business Media LLC ; 2018
    In:  Climate Dynamics Vol. 50, No. 1-2 ( 2018-1), p. 159-178
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 50, No. 1-2 ( 2018-1), p. 159-178
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-017-3594-0
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    Slow and fast annual cycles of the Asian summer monsoon in the NCEP CFSv2
    Springer Science and Business Media LLC ; 2016
    In:  Climate Dynamics Vol. 47, No. 1-2 ( 2016-7), p. 529-553
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 47, No. 1-2 ( 2016-7), p. 529-553
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-015-2854-0
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2016
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    Improved seasonal predictive skill and enhanced predictability of the Asian summer monsoon rainfall following ENSO events in NCEP CFSv2 hindcasts
    Springer Science and Business Media LLC ; 2019
    In:  Climate Dynamics Vol. 52, No. 5-6 ( 2019-3), p. 3079-3098
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 52, No. 5-6 ( 2019-3), p. 3079-3098
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-018-4316-y
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Verification of Land–Atmosphere Coupling in Forecast Models, Reanalyses, and Land Surface Models Using Flux Site Observations
    American Meteorological Society ; 2018
    In:  Journal of Hydrometeorology Vol. 19, No. 2 ( 2018-02-01), p. 375-392
    Details
    In: Journal of Hydrometeorology, American Meteorological Society, Vol. 19, No. 2 ( 2018-02-01), p. 375-392
    Abstract: This study compares four model systems in three configurations (LSM, LSM + GCM, and reanalysis) with global flux tower observations to validate states, surface fluxes, and coupling indices between land and atmosphere. Models clearly underrepresent the feedback of surface fluxes on boundary layer properties (the atmospheric leg of land–atmosphere coupling) and may overrepresent the connection between soil moisture and surface fluxes (the terrestrial leg). Models generally underrepresent spatial and temporal variability relative to observations, which is at least partially an artifact of the differences in spatial scale between model grid boxes and flux tower footprints. All models bias high in near-surface humidity and downward shortwave radiation, struggle to represent precipitation accurately, and show serious problems in reproducing surface albedos. These errors create challenges for models to partition surface energy properly, and errors are traceable through the surface energy and water cycles. The spatial distribution of the amplitude and phase of annual cycles (first harmonic) are generally well reproduced, but the biases in means tend to reflect in these amplitudes. Interannual variability is also a challenge for models to reproduce. Although the models validate better against Bowen-ratio-corrected surface flux observations, which allow for closure of surface energy balances at flux tower sites, it is not clear whether the corrected fluxes are more representative of actual fluxes. The analysis illuminates targets for coupled land–atmosphere model development, as well as the value of long-term globally distributed observational monitoring.
    Type of Medium: Online Resource
    ISSN: 1525-755X , 1525-7541
    URL: Article
    URL: Article
    DOI: 10.1175/JHM-D-17-0152.1
    DOI: 10.1175/JHM-D-17-0152.s1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 2042176-X
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  • 6
    Online Resource
    Online Resource
    Impact of Land Initial States Uncertainty on Subseasonal Surface Air Temperature Prediction in CFSv2 Reforecasts
    American Meteorological Society ; 2020
    In:  Journal of Hydrometeorology Vol. 21, No. 9 ( 2020-09-01), p. 2101-2121
    Details
    In: Journal of Hydrometeorology, American Meteorological Society, Vol. 21, No. 9 ( 2020-09-01), p. 2101-2121
    Abstract: The NCEP CFSv2 ensemble reforecasts initialized with different land surface analyses for the period of 1979–2010 have been conducted to assess the effect of uncertainty in land initial states on surface air temperature prediction. The two observation-based land initial states are adapted from the NCEP CFS Reanalysis (CFSR) and the NASA GLDAS-2 analysis; atmosphere, ocean, and ice initial states are identical for both reforecasts. This identical-twin experiment confirms that the prediction skill of surface air temperature is sensitive to the uncertainty of land initial states, especially in soil moisture and snow cover. There is no distinct characteristic that determines which set of the reforecasts performs better. Rather, the better performer varies with the lead week and location for each season. Estimates of soil moisture between the two land initial states are significantly different with an apparent north–south contrast for almost all seasons, causing predicted surface air temperature discrepancies between the two sets of reforecasts, particularly in regions where the magnitude of initial soil moisture difference lies in the top quintile. In boreal spring, inconsistency of snow cover between the two land initial states also plays a critical role in enhancing the discrepancy of predicted surface air temperature from week 5 to week 8. Our results suggest that a reduction of the uncertainty in land surface properties among the current land surface analyses will be beneficial to improving the prediction skill of surface air temperature on subseasonal time scales. Implications of a multiple land surface analysis ensemble are also discussed.
    Type of Medium: Online Resource
    ISSN: 1525-755X , 1525-7541
    URL: Article
    URL: Article
    DOI: 10.1175/JHM-D-20-0024.1
    DOI: 10.1175/jhm-d-20-0024.s1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 2042176-X
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  • 7
    Online Resource
    Online Resource
    Sensitivity of U.S. Drought Prediction Skill to Land Initial States
    American Meteorological Society ; 2020
    In:  Journal of Hydrometeorology Vol. 21, No. 12 ( 2020-12), p. 2793-2811
    Details
    In: Journal of Hydrometeorology, American Meteorological Society, Vol. 21, No. 12 ( 2020-12), p. 2793-2811
    Abstract: In addition to remote SST forcing, realistic representation of land forcing (i.e., soil moisture) over the United States is critical for a prediction of U.S. severe drought events approximately one season in advance. Using “identical twin” experiments with different land initial conditions (ICs) in the 32-yr (1979–2010) CFSv2 reforecasts (NASA GLDAS-2 reanalysis versus NCEP CFSR), sensitivity and skill of U.S. drought predictions to land ICs are evaluated. Although there is no outstanding performer between the two sets of forecasts with different land ICs, each set shows greater skill in some regions, but their locations vary with forecast lead time and season. The 1999 case study demonstrates that although a pattern of below-normal SSTs in the Pacific in the fall and winter is realistically reproduced in both reforecasts, GLDAS-2 land initial states display a stronger east–west gradient of soil moisture, particularly drier in the eastern United States and more consistent with observations, leading to warmer surface temperature anomalies over the United States. Anomalies lasting for one season are accompanied by more persistent barotropic (warm core) anomalous high pressure over CONUS, which results in better prediction skill of this drought case up to 4 months in advance in the reforecasts with GLDAS-2 land ICs. Therefore, it is essential to minimize the uncertainty of land initial states among the current land analyses for improving U.S. drought prediction on seasonal time scales.
    Type of Medium: Online Resource
    ISSN: 1525-755X , 1525-7541
    URL: Article
    URL: Article
    DOI: 10.1175/JHM-D-20-0025.1
    DOI: 10.1175/jhm-d-20-0025.s1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 2042176-X
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  • 8
    Online Resource
    Online Resource
    A Joint Approach Combining Correlation and Mutual Information to Study Land and Ocean Drivers of U.S. Droughts: Methodology
    American Meteorological Society ; 2023
    In:  Journal of Climate Vol. 36, No. 9 ( 2023-05-01), p. 2795-2814
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 36, No. 9 ( 2023-05-01), p. 2795-2814
    Abstract: Normalized mutual information (NMI) is a nonparametric measure of the dependence between two variables without assumptions about the shape of their bivariate data distributions, but the implementation and interpretation of NMI in the coupled climate system is more complicated than for linear correlations. This study presents a joint approach combining correlation and NMI to examine land and ocean surface forcing of U.S. drought at varying lead times. Based on the distribution of correlation versus NMI between a source variable (local or remote forcing) and target variable [e.g., summer precipitation in the southern Great Plains (SGP)], newly proposed one-tail significance levels for NMI combined with two-tailed significance levels of correlation enable us to discern linearity and nonlinearity dominant regimes in a more intuitive way. Our analysis finds that NMI can detect strong linear relationships like correlations, but it is not exclusively tuned to linear relationships as correlations are. Also, NMI can further identify nonlinear relationships, particularly when there are clusters and blank areas (high density and low density) in joint probability distributions between source and target variables (e.g., detected between soil moisture conditions in eastern Montana from mid-February to mid-August and summer precipitation in the SGP). The linear and nonlinear information are found to be sometimes mixed and rather convoluted with time, for instance, in the subtropical Pacific of the Southern Hemisphere, revealing relationships that cannot be fully detected by either NMI or correlation alone. Therefore, this joint approach is a potentially powerful tool to reveal complex and heretofore undetected relationships.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    URL: Article
    DOI: 10.1175/JCLI-D-22-0429.1
    DOI: 10.1175/JCLI-D-22-0429s1
    RVK:
    UA 4548
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2023
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 9
    Online Resource
    Online Resource
    Reforecasting the ENSO Events in the Past 57 Years (1958–2014)
    American Meteorological Society ; 2017
    In:  Journal of Climate Vol. 30, No. 19 ( 2017-10-01), p. 7669-7693
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 30, No. 19 ( 2017-10-01), p. 7669-7693
    Abstract: A set of ensemble seasonal reforecasts for 1958–2014 is conducted using the National Centers for Environmental Prediction (NCEP) Climate Forecast System, version 2. In comparison with other current reforecasts, this dataset extends the seasonal reforecasts to the 1960s–70s. Direct comparison of the predictability of the ENSO events occurring during the 1960s–70s with the more widely studied ENSO events since then demonstrates the seasonal forecast system’s capability in different phases of multidecadal variability and degrees of global climate change. A major concern for a long reforecast is whether the seasonal reforecasts before 1979 provide useful skill when observations, particularly of the ocean, were sparser. This study demonstrates that, although the reforecasts have lower skill in predicting SST anomalies in the North Pacific and North Atlantic before 1979, the prediction skill of the onset and development of ENSO events in 1958–78 is comparable to that for 1979–2014. In particular, the ENSO predictions initialized in April during 1958–78 show higher skill in the summer. However, the skill of the earlier predictions declines faster in the ENSO decaying phase, because the reforecasts initialized after boreal summer persistently predict lingering wind and SST anomalies over the eastern equatorial Pacific during such events. Reforecasts initialized in boreal fall overestimate the peak SST anomalies of strong El Niño events since the 1980s. Both phenomena imply that the model’s air–sea feedback is overly active in the eastern Pacific before ENSO event termination. Whether these differences are due to changes in the observing system or are associated with flow-dependent predictability remains an open question.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-16-0642.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2017
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 10
    Online Resource
    Online Resource
    A spurious warming trend in the NMME equatorial Pacific SST hindcasts
    Springer Science and Business Media LLC ; 2019
    In:  Climate Dynamics Vol. 53, No. 12 ( 2019-12), p. 7287-7303
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 53, No. 12 ( 2019-12), p. 7287-7303
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-017-3777-8
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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