Search Results
of the various boundary layer and cloud properties observed on the three cruises and highlight the differences between the three observational periods. Mean profiles of the MABL thermodynamic structure for each cruise for the period for which the research vessels remained stationed at the ORS location are also constructed and compared in section 3 . Section 4 discusses the physical properties of clouds and drizzle in an attempt to illuminate the various processes that modulate cloud life cycle
of the various boundary layer and cloud properties observed on the three cruises and highlight the differences between the three observational periods. Mean profiles of the MABL thermodynamic structure for each cruise for the period for which the research vessels remained stationed at the ORS location are also constructed and compared in section 3 . Section 4 discusses the physical properties of clouds and drizzle in an attempt to illuminate the various processes that modulate cloud life cycle
Dufresne 2005 ; Wood et al. 2009 ). Despite their importance, climate models often underestimate low cloud cover but overestimate their optical thickness ( Nam et al. 2012 ; Bony and Dufresne 2005 ) and simulate different signs and magnitudes of the low cloud feedback ( Zelinka et al. 2020 ; Vial et al. 2013 ; Bony and Dufresne 2005 ). MBL clouds frequently produce precipitation, most often in the form of drizzle ( Wood 2012 ; Rémillard et al. 2012 ; Dong et al. 2014a ; Wu et al. 2015 , 2017
Dufresne 2005 ; Wood et al. 2009 ). Despite their importance, climate models often underestimate low cloud cover but overestimate their optical thickness ( Nam et al. 2012 ; Bony and Dufresne 2005 ) and simulate different signs and magnitudes of the low cloud feedback ( Zelinka et al. 2020 ; Vial et al. 2013 ; Bony and Dufresne 2005 ). MBL clouds frequently produce precipitation, most often in the form of drizzle ( Wood 2012 ; Rémillard et al. 2012 ; Dong et al. 2014a ; Wu et al. 2015 , 2017
precipitation and drizzle as a prominent component of MBL clouds, which suggests the potential importance of this precipitation in Earth’s cloud and radiation budgets. Remote sensors such as Doppler cloud radars (e.g., Ka band and W band), ceilometers, and microwave radiometers, in addition to in situ sampling using radiosondes and research aircraft have provided detailed measurements over windows of time ranging from a month or two to over one year, occasionally during different seasons in each location or
precipitation and drizzle as a prominent component of MBL clouds, which suggests the potential importance of this precipitation in Earth’s cloud and radiation budgets. Remote sensors such as Doppler cloud radars (e.g., Ka band and W band), ceilometers, and microwave radiometers, in addition to in situ sampling using radiosondes and research aircraft have provided detailed measurements over windows of time ranging from a month or two to over one year, occasionally during different seasons in each location or
1. Introduction Drizzle occurrence can provide important insight into the dynamics and microphysics of low-level clouds (e.g., Stevens et al. 2005 ). Many previous drizzle studies have focused on the effect of cloud condensation nuclei on the growth and size distribution of drizzle droplets in marine stratocumulus and stratus clouds (e.g., Frisch et al. 1995 ; Feingold et al. 1996 , 1999 ; Gerber 1996 ; Galloway et al. 1999 ; Ferek et al. 2000 ; Hudson and Yum 2001 ; Rasmussen et al
1. Introduction Drizzle occurrence can provide important insight into the dynamics and microphysics of low-level clouds (e.g., Stevens et al. 2005 ). Many previous drizzle studies have focused on the effect of cloud condensation nuclei on the growth and size distribution of drizzle droplets in marine stratocumulus and stratus clouds (e.g., Frisch et al. 1995 ; Feingold et al. 1996 , 1999 ; Gerber 1996 ; Galloway et al. 1999 ; Ferek et al. 2000 ; Hudson and Yum 2001 ; Rasmussen et al
simulations. In Fig. 1 , we compare the mean precipitation from the 17 CMIP6 models for the historical period to the mean observed precipitation, computed as the average of TRMM and PERSIANN precipitation. Compared to observations, the CMIP6 multimodel mean shows excessive precipitation over the tropical oceans off the equator and drier conditions over the tropical landmasses. Figure 2 shows the climatological mean of the daily low-intensity precipitation, or drizzle, and evaporation. For reasons that
simulations. In Fig. 1 , we compare the mean precipitation from the 17 CMIP6 models for the historical period to the mean observed precipitation, computed as the average of TRMM and PERSIANN precipitation. Compared to observations, the CMIP6 multimodel mean shows excessive precipitation over the tropical oceans off the equator and drier conditions over the tropical landmasses. Figure 2 shows the climatological mean of the daily low-intensity precipitation, or drizzle, and evaporation. For reasons that
precipitation rate. Compared to observations that feature intermittent periods of precipitation and no precipitation, GCMs simulate too infrequent periods of no precipitation, too frequent drizzle and light precipitation, and too little heavy precipitation ( Dai 2006 ; Stephens et al. 2010 ; Trenberth and Zhang 2018 ; Fiedler et al. 2020 ). These model biases in local-scale precipitation characteristics are often referred to as “the drizzling bias,” which is expected to influence cloud formation and
precipitation rate. Compared to observations that feature intermittent periods of precipitation and no precipitation, GCMs simulate too infrequent periods of no precipitation, too frequent drizzle and light precipitation, and too little heavy precipitation ( Dai 2006 ; Stephens et al. 2010 ; Trenberth and Zhang 2018 ; Fiedler et al. 2020 ). These model biases in local-scale precipitation characteristics are often referred to as “the drizzling bias,” which is expected to influence cloud formation and
al. 2012 ), mesoscale circulations ( Atkinson and Zhang 1996 ), drizzle ( vanZanten and Stevens 2005 ; Comstock et al. 2005 ; Wood and Hartmann 2006 ), near-surface outflow boundaries and density currents ( Feingold et al. 2010 ; Terai 2011 ; Wilbanks 2013 ), aerosols ( Albrecht 1989 ; Pincus and Baker 1994 ), boundary layer depth ( Bretherton and Wyant 1997 ; Wood and Hartmann 2006 ; Mechem et al. 2012 ), and gravity waves ( Allen et al. 2013 ). Mesoscale transitions (in both directions
al. 2012 ), mesoscale circulations ( Atkinson and Zhang 1996 ), drizzle ( vanZanten and Stevens 2005 ; Comstock et al. 2005 ; Wood and Hartmann 2006 ), near-surface outflow boundaries and density currents ( Feingold et al. 2010 ; Terai 2011 ; Wilbanks 2013 ), aerosols ( Albrecht 1989 ; Pincus and Baker 1994 ), boundary layer depth ( Bretherton and Wyant 1997 ; Wood and Hartmann 2006 ; Mechem et al. 2012 ), and gravity waves ( Allen et al. 2013 ). Mesoscale transitions (in both directions
Abstract
In this study, daily precipitation (P) records for 1960–2013 from 632 stations in China were homogenized and then applied to study the changes in the frequency of dry (P = 0) and trace (0 < P < 0.1 mm day−1) days and all precipitation events (P ≥ 0.1 mm day−1), and the frequency and accumulated amount of precipitation at different intensities. Over China as a whole, very heavy precipitation (P ≥ 50 mm day) events have increased significantly from 1960 to 2013, while light (0.1 ≤ P < 10 mm day−1) and moderate (10 ≤ P < 25 mm day−1) events have decreased significantly, accompanying the significant increases of dry days and decreases of trace days. This indicates a shift from light to intense precipitation, implying increased risks of drought and floods over China since 1960. Although the consistent increases of dry days and decreases of trace days and light and total precipitation days are seen over most of China, changes in other precipitation categories exhibit clear regional differences. Over the Yangtze River valley and southeast China, very heavy precipitation events have increased while light precipitation events have decreased. However, positive trends are seen for all precipitation categories over northwest China, while trends are generally negative over southwest, northeast, and northern China. To examine the association with global warming, the dependence of the precipitation change for each intensity category over China on global-mean temperature was analyzed using interannual to decadal variations. Results show that dry and trace days and very light and very heavy precipitation events exhibit larger changes per unit global warming than medium-intensity precipitation events.
Abstract
In this study, daily precipitation (P) records for 1960–2013 from 632 stations in China were homogenized and then applied to study the changes in the frequency of dry (P = 0) and trace (0 < P < 0.1 mm day−1) days and all precipitation events (P ≥ 0.1 mm day−1), and the frequency and accumulated amount of precipitation at different intensities. Over China as a whole, very heavy precipitation (P ≥ 50 mm day) events have increased significantly from 1960 to 2013, while light (0.1 ≤ P < 10 mm day−1) and moderate (10 ≤ P < 25 mm day−1) events have decreased significantly, accompanying the significant increases of dry days and decreases of trace days. This indicates a shift from light to intense precipitation, implying increased risks of drought and floods over China since 1960. Although the consistent increases of dry days and decreases of trace days and light and total precipitation days are seen over most of China, changes in other precipitation categories exhibit clear regional differences. Over the Yangtze River valley and southeast China, very heavy precipitation events have increased while light precipitation events have decreased. However, positive trends are seen for all precipitation categories over northwest China, while trends are generally negative over southwest, northeast, and northern China. To examine the association with global warming, the dependence of the precipitation change for each intensity category over China on global-mean temperature was analyzed using interannual to decadal variations. Results show that dry and trace days and very light and very heavy precipitation events exhibit larger changes per unit global warming than medium-intensity precipitation events.
GCM. The physical processes that are responsible for structures seen in the MBL cloud fields are not fully understood, but recent research has indicated that the occurrence of drizzle may play a key role in forming and sustaining the observed structures. Observational studies have investigated pockets of open cells (POCs) that are embedded in otherwise uniform stratocumulus, and resemble broader regions of open mesoscale cellular convection typically found farther offshore ( Stevens et al. 2005
GCM. The physical processes that are responsible for structures seen in the MBL cloud fields are not fully understood, but recent research has indicated that the occurrence of drizzle may play a key role in forming and sustaining the observed structures. Observational studies have investigated pockets of open cells (POCs) that are embedded in otherwise uniform stratocumulus, and resemble broader regions of open mesoscale cellular convection typically found farther offshore ( Stevens et al. 2005
studied on a global scale. In this study, we analyze the present weather reports from station and ship observations to derive a near-global (50°S–70°N) climatology of the diurnal cycle of the frequency of occurrence 1 for various types of precipitation (drizzle, nondrizzle, showery, nonshowery, and snow) and thunderstorms. Despite many potential biases in the weather reports, they represent one of a few in situ observations of precipitation characteristics on a global scale ( Dai 2001 ). Our results
studied on a global scale. In this study, we analyze the present weather reports from station and ship observations to derive a near-global (50°S–70°N) climatology of the diurnal cycle of the frequency of occurrence 1 for various types of precipitation (drizzle, nondrizzle, showery, nonshowery, and snow) and thunderstorms. Despite many potential biases in the weather reports, they represent one of a few in situ observations of precipitation characteristics on a global scale ( Dai 2001 ). Our results
