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- Author or Editor: Norman J. Rosenberg x
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Abstract
Turbulent fluctuations of vertical wind and fluxes of momentum, sensible heat and latent heat measured with a drag anemometer are compared to like data measured with other instruments. Means of the measured parameters agreed well with energy balance computations of the heat fluxes and profile measurements of the momentum flux. Drag anemometer measurements of turbulent fluxes generally exceeded those obtained with a propeller anemometer, run concurrently. Spectral analysis indicates that the propeller anemometer did not respond well at high frequencies, causing an underestimation of the fluxes and vertical wind fluctuations. The drag anemometer appears to respond well up to 5 Hz.
Abstract
Turbulent fluctuations of vertical wind and fluxes of momentum, sensible heat and latent heat measured with a drag anemometer are compared to like data measured with other instruments. Means of the measured parameters agreed well with energy balance computations of the heat fluxes and profile measurements of the momentum flux. Drag anemometer measurements of turbulent fluxes generally exceeded those obtained with a propeller anemometer, run concurrently. Spectral analysis indicates that the propeller anemometer did not respond well at high frequencies, causing an underestimation of the fluxes and vertical wind fluctuations. The drag anemometer appears to respond well up to 5 Hz.
Abstract
Spectra of vertical and horizontal velocity, air temperature and humidity fluctuations were analyzed from measurements made over a well-watered alfalfa crop under conditions of sensible heat advection. Vertical velocity and air temperature spectra as well as cospectra of momentum, sensible heat and water vapor were found to be dependent on atmospheric thermal stratification. These spectra and cospectra were shifted toward higher frequencies under advective as compared to lapse conditions. These results indicate that the predominant eddy sizes are relatively smaller under advective conditions. Humidity spectra, on the other hand, were independent of daytime thermal stratification conditions but were influenced by conditions of the crop. The humidity spectra over a transpiring crop were shifted toward lower frequencies as compared to those over a less well-developed crop canopy.
Abstract
Spectra of vertical and horizontal velocity, air temperature and humidity fluctuations were analyzed from measurements made over a well-watered alfalfa crop under conditions of sensible heat advection. Vertical velocity and air temperature spectra as well as cospectra of momentum, sensible heat and water vapor were found to be dependent on atmospheric thermal stratification. These spectra and cospectra were shifted toward higher frequencies under advective as compared to lapse conditions. These results indicate that the predominant eddy sizes are relatively smaller under advective conditions. Humidity spectra, on the other hand, were independent of daytime thermal stratification conditions but were influenced by conditions of the crop. The humidity spectra over a transpiring crop were shifted toward lower frequencies as compared to those over a less well-developed crop canopy.
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ABSTRACT
The Missouri River basin (MRB) is the largest river basin in the United States and is one of the most important agricultural regions in the world. Three decadal climate variability (DCV) phenomena—the Pacific decadal oscillation (PDO), the tropical Atlantic sea surface temperature (SST) gradient variability (TAG), and the west Pacific warm pool SST variability (WPWP)—substantially influence hydrometeorology in the MRB. The authors report on a simulation study with the Soil and Water Assessment Tool (SWAT) to estimate impacts on water availability in response to realistic values of PDO, TAG, and WPWP indices in approximately 13 500 hydrologic unit areas covering the MRB. SWAT, driven by hydrometeorological anomalies associated with positive and negative phases of PDO and TAG, indicated major impacts on water yields and streamflows, as much as ±40% of the average in many locations. Impacts of the WPWP index were smaller. Consistent with observations during 1949–2010, SWAT showed water flow increases of as much as 80% of the average, causing very wet periods when the positive phase of the PDO and the negative phase of the TAG at extreme amplitudes were superposed. Water flows decreased by a similar amount, resulting in severe to extreme droughts when the negative phase of the PDO and the positive phase of the TAG at extreme amplitudes were superposed. Thus, the combined and cumulative effects of these DCV phenomena on water flows, droughts, and wet periods in the MRB can be dramatic, with important consequences for all water-consuming sectors as well as for feedbacks to the climate system.
ABSTRACT
The Missouri River basin (MRB) is the largest river basin in the United States and is one of the most important agricultural regions in the world. Three decadal climate variability (DCV) phenomena—the Pacific decadal oscillation (PDO), the tropical Atlantic sea surface temperature (SST) gradient variability (TAG), and the west Pacific warm pool SST variability (WPWP)—substantially influence hydrometeorology in the MRB. The authors report on a simulation study with the Soil and Water Assessment Tool (SWAT) to estimate impacts on water availability in response to realistic values of PDO, TAG, and WPWP indices in approximately 13 500 hydrologic unit areas covering the MRB. SWAT, driven by hydrometeorological anomalies associated with positive and negative phases of PDO and TAG, indicated major impacts on water yields and streamflows, as much as ±40% of the average in many locations. Impacts of the WPWP index were smaller. Consistent with observations during 1949–2010, SWAT showed water flow increases of as much as 80% of the average, causing very wet periods when the positive phase of the PDO and the negative phase of the TAG at extreme amplitudes were superposed. Water flows decreased by a similar amount, resulting in severe to extreme droughts when the negative phase of the PDO and the positive phase of the TAG at extreme amplitudes were superposed. Thus, the combined and cumulative effects of these DCV phenomena on water flows, droughts, and wet periods in the MRB can be dramatic, with important consequences for all water-consuming sectors as well as for feedbacks to the climate system.
Abstract
Many decadal climate prediction efforts have been initiated under phase 5 of the World Climate Research Programme Coupled Model Intercomparison Project. There is considerable ongoing discussion about model deficiencies, initialization techniques, and data requirements, but not much attention is being given to decadal climate information (DCI) needs of stakeholders for decision support. Here, the authors report the results of exploratory activities undertaken to assess DCI needs in water resources and agriculture sectors, using the Missouri River basin as a case study. This assessment was achieved through discussions with 120 stakeholders.
Stakeholders’ awareness of decadal dry and wet spells and their societal impacts in the basin are described, and stakeholders’ DCI needs and potential barriers to their use of DCI are enumerated. The authors find that impacts, including economic impacts, of decadal climate variability (DCV) on water and agricultural production in the basin are distinctly identifiable and characterizable. Stakeholders have clear notions about their needs for DCI and have offered specific suggestions as to how these might be met. However, while stakeholders are eager to have climate information, including decadal climate outlooks (DCOs), there are many barriers to the use of such information. The first and foremost barrier is that the credibility of DCOs is yet to be established. Second, the nature of institutional rules and regulations, laws, and legal precedents that pose obstacles to the use of DCOs must be better understood and means to modify these, where possible, must be sought. For the benefit of climate scientists, these and other stakeholder needs are also articulated in this paper.
Abstract
Many decadal climate prediction efforts have been initiated under phase 5 of the World Climate Research Programme Coupled Model Intercomparison Project. There is considerable ongoing discussion about model deficiencies, initialization techniques, and data requirements, but not much attention is being given to decadal climate information (DCI) needs of stakeholders for decision support. Here, the authors report the results of exploratory activities undertaken to assess DCI needs in water resources and agriculture sectors, using the Missouri River basin as a case study. This assessment was achieved through discussions with 120 stakeholders.
Stakeholders’ awareness of decadal dry and wet spells and their societal impacts in the basin are described, and stakeholders’ DCI needs and potential barriers to their use of DCI are enumerated. The authors find that impacts, including economic impacts, of decadal climate variability (DCV) on water and agricultural production in the basin are distinctly identifiable and characterizable. Stakeholders have clear notions about their needs for DCI and have offered specific suggestions as to how these might be met. However, while stakeholders are eager to have climate information, including decadal climate outlooks (DCOs), there are many barriers to the use of such information. The first and foremost barrier is that the credibility of DCOs is yet to be established. Second, the nature of institutional rules and regulations, laws, and legal precedents that pose obstacles to the use of DCOs must be better understood and means to modify these, where possible, must be sought. For the benefit of climate scientists, these and other stakeholder needs are also articulated in this paper.
