scholarly journals H<sub>2</sub> vertical profiles in the continental boundary layer: measurements at the Cabauw tall tower in The Netherlands

2011 ◽  
Vol 11 (13) ◽  
pp. 6425-6443 ◽  
Author(s):  
M. E. Popa ◽  
A. T. Vermeulen ◽  
W. C. M. van den Bulk ◽  
P. A. C. Jongejan ◽  
A. M. Batenburg ◽  
...  
Keyword(s):  
Boundary Layer ◽  
The Netherlands ◽  
Large Scale ◽  
Ground Level ◽  
Vertical Profiles ◽  
Short Term ◽  
Soil Uptake ◽  
Sampling Height ◽  
Tall Tower

Abstract. In-situ, quasi-continuous measurements of atmospheric hydrogen (H2) have been performed since October 2007 at the Cabauw tall tower station in the Netherlands. Mole fractions of H2, CO and several greenhouse gases are determined simultaneously in air sampled successively at four heights, between 20 and 200 m above ground level. 222Rn measurements are performed in air sampled at 20 and 200 m. This H2 dataset represents the first in-situ, quasi-continuous long-term measurement series of vertical profiles of H2 in the lower continental boundary layer. Seasonal cycles are present at all heights in both H2 and CO, and their amplitude varies with the sampling height. The seasonality is evident in both the "baseline" values and in the short term (diurnal to synoptic time scales) variability, the latter being significantly larger during winter. The observed H2 short term signals and vertical gradients are in many cases well correlated to other species, especially to CO. On the other hand, H2 has at times a unique behaviour, due to its particular distribution of sources and sinks. Our estimation for the regional H2 soil uptake flux, using the radon tracer method, is (−1.89 ± 0.26) × 10−5 g/(m2 h), significantly smaller than other recent results from Europe. H2/CO ratios of the traffic emissions computed from our data, with an average of 0.54 ± 0.07 mol:mol, are larger and more variable than estimated in some of the previous studies in Europe. This difference can be explained by a different driving regime, due to the frequent traffic jams in the influence area of Cabauw. The H2/CO ratios of the large scale pollution events have an average of 0.36 ± 0.05 mol:mol; these ratios were observed to slightly increase with sampling height, possibly due to a stronger influence of soil uptake at the lower sampling heights.

scholarly journals H<sub>2</sub> vertical profiles in the continental boundary layer: measurements at the Cabauw tall tower in the Netherlands

2011 ◽  
Vol 11 (2) ◽  
pp. 5589-5639 ◽  
Author(s):  
M. E. Popa ◽  
A. T. Vermeulen ◽  
W. C. M. van den Bulk ◽  
P. A. C. Jongejan ◽  
A. M. Batenburg ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ground Level ◽  
The Other ◽  
Vertical Profiles ◽  
Short Term ◽  
Soil Uptake ◽  
Sampling Height ◽  
Vertical Gradients ◽  
Tall Tower

Abstract. In-situ, quasi-continuous measurements of atmospheric hydrogen (H2) have been performed since 2007 at the Cabauw tall tower station in the Netherlands. Mole fractions of H2, CO and several greenhouse gases are determined simultaneously in air sampled successively at four heights, between 20 and 200 m above ground level. 222Rn measurements are performed in air sampled at 20 and 200 m. This H2 dataset represents the first in-situ, quasi-continuous measurement series of vertical profiles of H2 in the lower continental boundary layer. From the three-year long time series, we characterize the main features and variability patterns of H2 and CO on various time scales; the time series is too short to justify an attempt to determine multi-annual trends. Seasonal cycles are present in both H2 and CO, and their amplitude varies with the sampling height. The seasonality is evident in both the "baseline" values and in the short term (diurnal to synoptic time scales) variability, the latter being significantly larger during winter. The observed H2 short term signals and vertical gradients are in many cases well correlated to other species, especially to CO. On the other hand, H2 has at times a behaviour which differentiates it from all the other species measured, due to its particular distribution of sources and sinks, that is, with the main source in our area (anthropogenic emissions) and the main sink (soil uptake) both near ground level. The local to regional soil sink of H2 is observable as H2 depletion at the lower sampling levels in some of the stable nights, although the signals at Cabauw are smaller than observed at other stations. Positive vertical gradients are another consequence of the soil uptake. Our estimation for the regional H2 soil uptake flux, using the radon tracer method, is (−1.89 ± 0.26) × 10−5 g/(m2h), significantly smaller than other recent results from Europe. Local soil and weather characteristics might be responsible for the very low soil uptake of H2. Our result could also be biased by the absence of radon flux estimates that could reliably approximate the fluxes during the relevant time intervals in our study domain. H2/CO ratios of the traffic emissions computed from our data, with an average of 0.54 ± 0.07 mol:mol, are larger and more scattered than estimated in some of the previous studies in Europe. This difference can be explained by a different driving regime, due to the frequent traffic jams in the influence area of Cabauw. In contrast, the H2/CO ratios of the large scale pollution events, with an average of 0.36 ± 0.05 mol:mol, are very similar to results of previous studies; these ratios were observed to slightly increase with sampling height, possibly due to a stronger influence of soil uptake at the lower sampling heights.

scholarly journals Observed Evolution of Northward-Propagating Intraseasonal Variation over the Western Pacific: A Case Study in Boreal Early Summer

2013 ◽  
Vol 141 (2) ◽  
pp. 690-706 ◽  
Author(s):  
Masaki Katsumata ◽  
Hiroyuki Yamada ◽  
Hisayuki Kubota ◽  
Qoosaku Moteki ◽  
Ryuichi Shirooka
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Lower Troposphere ◽  
Western Pacific ◽  
Boreal Summer ◽  
Intraseasonal Variation ◽  
Middle Troposphere ◽  
Inactive Period ◽  
The Western Pacific

Abstract This report describes the in situ observed evolution of the atmospheric profile during an event of the boreal summer intraseasonal variation (BSISV) in the tropical western Pacific Ocean. The convectively active region of the BSISV proceeded northward over the sounding and radar network. Over the array, the situation changed from a convectively inactive period to an active period. Inspection of the sounding data revealed the gradual moistening of the lower troposphere during the convectively inactive period. The sounding-derived heat and moisture budget analyses indicated that both the convective- and large-scale processes caused moistening of the lower and middle troposphere where the radar echo tops were observed most frequently. This study is the first to identify such a “preconditioning” process for the BSISV in the western Pacific using detailed in situ observational data. During the preconditioning, an increase in CAPE was observed, as in previous studies of the MJO. An increase of moisture in the boundary layer was responsible for the increase of CAPE. The large-scale horizontal convergence in the boundary layer may be a key factor to moisten the boundary layer through the convective-scale processes, as well as through the large-scale processes to moisten the lower and middle troposphere.

scholarly journals Automated ground-based remote sensing measurements of greenhouse gases at the Białystok site in comparison with collocated in situ measurements and model data

2012 ◽  
Vol 12 (15) ◽  
pp. 6741-6755 ◽  
Author(s):  
J. Messerschmidt ◽  
H. Chen ◽  
N. M. Deutscher ◽  
C. Gerbig ◽  
P. Grupe ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Boundary Layer ◽  
Lower Troposphere ◽  
Fourier Transform Spectrometer ◽  
Model Data ◽  
Solar Absorption ◽  
Near Surface ◽  
Tall Tower ◽  
Absorption Measurements

Abstract. The in situ boundary layer measurement site in Białystok (Poland) has been upgraded with a fully automated observatory for total greenhouse gas column measurements. The automated Fourier Transform Spectrometer (FTS) complements the on-site in situ facilities and FTS solar absorption measurements have been recorded nearly continuously in clear and partially cloudy conditions since March 2009. Here, the FTS measurements are compared with the collocated tall tower data. Additionally, simulations of the Jena CO2 inversion model are evaluated with the Białystok measurement facilities. The simulated seasonal CO2 cycle is slightly overestimated by a mean difference of 1.2 ppm ± 0.9 ppm (1σ) in comparison with the FTS measurements. CO2 concentrations at the surface, measured at the tall tower (5 m, 90 m, 300 m), are slightly underestimated by −1.5 ppm, −1.6 ppm, and −0.7 ppm respectively during the day and by −9.1 ppm, −5.9 ppm, and −1.3 ppm during the night. The comparison of the simulated CO2 profiles with low aircraft profiles shows a slight overestimation of the lower troposphere (by up to 1 ppm) and an underestimation in near-surface heights until 800 m (by up to 2.5 ppm). In an appendix the automated FTS observatory, including the hardware components and the automation software, is described in its basics.

scholarly journals A case of extreme particulate matter concentrations over Central Europe caused by dust emitted over the southern Ukraine

2008 ◽  
Vol 8 (4) ◽  
pp. 997-1016 ◽  
Author(s):  
W. Birmili ◽  
K. Schepanski ◽  
A. Ansmann ◽  
G. Spindler ◽  
I. Tegen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particulate Matter ◽  
Central Europe ◽  
Large Scale ◽  
Dust Emission ◽  
Wavelength Dependence ◽  
Light Extinction ◽  
Crustal Material ◽  
Southern Ukraine

Abstract. On 24 March 2007, an extraordinary dust plume was observed in the Central European troposphere. Satellite observations revealed its origins in a dust storm in Southern Ukraine, where large amounts of soil were resuspended from dried-out farmlands at wind gusts up to 30 m s−1. Along the pathway of the plume, maximum particulate matter (PM10) mass concentrations between 200 and 1400 μg m−3 occurred in Slovakia, the Czech Republic, Poland, and Germany. Over Germany, the dust plume was characterised by a volume extinction coefficient up to 400 Mm−1 and a particle optical depth of 0.71 at wavelength 0.532 μm. In-situ size distribution measurements as well as the wavelength dependence of light extinction from lidar and Sun photometer measurements confirmed the presence of a coarse particle mode with diameters around 2–3 μm. Chemical particle analyses suggested a fraction of 75% crustal material in daily average PM10 and up to 85% in the coarser fraction PM10–2.5. Based on the particle characteristics as well as a lack of increased CO and CO2 levels, a significant impact of biomass burning was ruled out. The reasons for the high particle concentrations in the dust plume were twofold: First, dust was transported very rapidly into Central Europe in a boundary layer jet under dry conditions. Second, the dust plume was confined to a relatively stable boundary layer of 1.4–1.8 km height, and could therefore neither expand nor dilute efficiently. Our findings illustrate the capacity of combined in situ and remote sensing measurements to characterise large-scale dust plumes with a variety of aerosol parameters. Although such plumes from Southern Eurasia seem to occur rather infrequently in Central Europe, its unexpected features highlights the need to improve the description of dust emission, transport and transformation processes needs, particularly when facing the possible effects of further anthropogenic desertification and climate change.

scholarly journals The CU Airborne MAX-DOAS instrument: vertical profiling of aerosol extinction and trace gases

2013 ◽  
Vol 6 (3) ◽  
pp. 719-739 ◽  
Author(s):  
S. Baidar ◽  
H. Oetjen ◽  
S. Coburn ◽  
B. Dix ◽  
I. Ortega ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Spatial Scales ◽  
Trace Gases ◽  
Stray Light ◽  
Aerosol Extinction ◽  
Vertical Profiles ◽  
Maximum Information ◽  
Extinction Coefficients

Abstract. The University of Colorado Airborne Multi-Axis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS) instrument uses solar stray light to detect and quantify multiple trace gases, including nitrogen dioxide (NO2), glyoxal (CHOCHO), formaldehyde (HCHO), water vapor (H2O), nitrous acid (HONO), iodine monoxide (IO), bromine monoxide (BrO), and oxygen dimers (O4) at multiple wavelengths (absorption bands at 360, 477, 577, 632 nm) simultaneously in the open atmosphere. The instrument is unique as it (1) features a motion compensation system that decouples the telescope field of view from aircraft movements in real time (<0.35° accuracy), and (2) includes measurements of solar stray light photons from nadir, zenith, and multiple elevation angles forward and below the plane by the same spectrometer/detector system. Sets of solar stray light spectra collected from nadir to zenith scans provide some vertical profile information within 2 km above and below the aircraft altitude, and the vertical column density (VCD) below the aircraft is measured in nadir view. Maximum information about vertical profiles is derived simultaneously for trace gas concentrations and aerosol extinction coefficients over similar spatial scales and with a vertical resolution of typically 250 m during aircraft ascent/descent. The instrument is described, and data from flights over California during the CalNex (California Research at the Nexus of Air Quality and Climate Change) and CARES (Carbonaceous Aerosols and Radiative Effects Study) air quality field campaigns is presented. Horizontal distributions of NO2 VCD (below the aircraft) maps are sampled with typically 1 km resolution, and show good agreement with two ground-based MAX-DOAS instruments (slope = 0.95 ± 0.09, R2 = 0.86). As a case study vertical profiles of NO2, CHOCHO, HCHO, and H2O concentrations and aerosol extinction coefficients, ε, at 477 nm calculated from O4 measurements from a low approach at Brackett airfield inside the South Coast Air Basin (SCAB) are presented. These profiles contain ~12 degrees of freedom (DOF) over a 3.5 km altitude range, an independent information approximately every 250 m. The boundary layer NO2 concentration, and the integral aerosol extinction over height (aerosol optical depth, AOD) agrees well with nearby ground-based in situ NO2 measurement, and AERONET station. The detection limits of NO2, CHOCHO, HCHO, H2O442, &amp;varepsilon;360, &amp;varepsilon;477 for 30 s integration time spectra recorded forward of the plane are 5 ppt, 3 ppt, 100 ppt, 42 ppm, 0.004 km−1, 0.002 km−1 in the free troposphere (FT), and 30 ppt, 16 ppt, 540 ppt, 252 ppm, 0.012 km−1, 0.006 km−1 inside the boundary layer (BL), respectively. Mobile column observations of trace gases and aerosols are complimentary to in situ observations, and help bridge the spatial scales that are probed by satellites and ground-based observations, and predicted by atmospheric models.

scholarly journals Six years of high-precision quasi-continuous atmospheric greenhouse gas measurements at Trainou Tower (Orléans Forest, France)

2014 ◽  
Vol 7 (1) ◽  
pp. 569-604 ◽  
Author(s):  
M. Schmidt ◽  
M. Lopez ◽  
C. Yver Kwok ◽  
C. Messager ◽  
M. Ramonet ◽  
...  
Keyword(s):  
In Situ Measurements ◽  
Atmospheric Measurements ◽  
Short Term ◽  
Gas Detector ◽  
Sampling Height ◽  
The Mean ◽  
Drying System ◽  
Gas Measurements ◽  
Television Tower

Abstract. Results from the Trainou tall tower measurement station installed in 2006, are presented for atmospheric measurements of CO2, CH4, N2O, SF6, CO, H2 mole fractions and Radon-222 activity. Air is sampled from four sampling heights (180 m, 100 m, 50 m and 5 m) of the Trainou 200 m television tower in the Orléans forest in France (47°57'53'' N, 2°06'45'' E, 131 m a.s.l.). The station is equipped with a custom-build CO2 analyzer (CARIBOU), which is based on a commercial NDIR analyser (Licor 6252), and a coupled gas chromatographic GC system equipped with ECD and FID (HP6890N, Agilent) and a reduction gas detector (PP1, Peak Performer). Air intakes, pumping and air drying system are shared between the CARIBOU and the GC systems. After some initial problems, we achieved short-term repeatability (1 sigma, over several days) for the GC system of of 0.05 ppm for CO2, 1.4 ppb for CH4, 0.25 ppb for N2O, 0.08 ppb for SF6, 0.88 ppb for CO and 3.8 for H2. The repeatability of the CARIBOU CO2 analyser is 0.06 ppm. In addition to the in-situ measurements, weekly flask sampling is performed, and flask air samples are analysed at the LSCE central laboratory for the same species as well for stable isotopes of CO2. The comparison between in-situ measurements and the flask sampling showed averaged differences of 0.08 ± 1.4 ppm CO2, 0.69 ± 7.3 ppb CH4, 0.64 ± 0.62 ppb N2O, 0.01 ± 0.1 ppt SF6 and 1.5 ± 5.3 ppb CO for the years 2008–2012. At Trainou station, the mean annual increase rates from 2007 to 2011 at the 180 m sampling height were 2.2 ppm yr−1 for CO2, 4 ppb yr−1 for CH4, 0.78 ppb yr−1 for N2O and 0.29 ppt yr−1 for SF6 respectively. For all species the 180 m sampling level showed the smallest diurnal variation. Mean diurnal gradients between the 50 m and the 180 m sampling level reached up to 30 ppm CO2, 15 ppm CH4 or 0.5 ppb N2O during night whereas the mean gradients are smaller than 0.5 ppm for CO2 and 1.5 ppb for CH4 during afternoon.

scholarly journals Variation of CO<sub>2</sub> mole fraction in the lower free troposphere, in the boundary layer and at the surface

2012 ◽  
Vol 12 (5) ◽  
pp. 11539-11566 ◽  
Author(s):  
L. Haszpra ◽  
M. Ramonet ◽  
M. Schmidt ◽  
Z. Barcza ◽  
Z. Pátkai ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Mole Fraction ◽  
Seasonal Cycle ◽  
Marine Boundary Layer ◽  
Mixed Boundary ◽  
Monitoring Site ◽  
Vertical Profiles ◽  
Free Atmosphere ◽  
Seasonal Behavior ◽  
Tall Tower

Abstract. Eight years of occasional flask air sampling and 3 yr of frequent in situ measurements of carbon dioxide (CO2) vertical profiles on board of a small aircraft, over a tall tower greenhouse gases monitoring site in Hungary are used for the analysis of the variations of vertical profile of CO2 mole fraction. Using the airborne vertical profiles and the measurements along the 115 m tall tower it is shown that the measurements at the top of the tower estimate the mean boundary layer CO2 mole fraction during the mid-afternoon fairly well, with an underestimation of 0.27–0.85 μmol mol−1 in summer, and an overestimation of 0.66–1.83 μmol mol−1 in winter. The seasonal cycle of CO2 mole fraction is damped with elevation. While the amplitude of the seasonal cycle is 28.5 μmol mol−1 at 10 m above the ground, it is only 10.7 μmol mol−1 in the layer of 2500–3000 m corresponding to the lower free atmosphere above the well-mixed boundary layer. The maximum mole fraction in the layer of 2500–3000 m can be observed around 25 March on average, two weeks ahead of that of the marine boundary layer reference (GLOBALVIEW). By contrast, close to the ground, the maximum CO2 mole fraction is observed late December, early January. The specific seasonal behavior is attributed to the climatology of vertical mixing of the atmosphere in the Carpathian Basin.

scholarly journals The vertical variability of black carbon observed in the atmospheric boundary layer during DACCIWA

2020 ◽  
Vol 20 (13) ◽  
pp. 7911-7928 ◽  
Author(s):  
Barbara Altstädter ◽  
Konrad Deetz ◽  
Bernhard Vogel ◽  
Karmen Babić ◽  
Cheikh Dione ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Black Carbon ◽  
West African Monsoon ◽  
Ground Level ◽  
Cloud Base ◽  
Small Scale ◽  
Vertical Profiles ◽  
Scale Modelling ◽  
Reactive Trace Gases

Abstract. This study underlines the important role of the transported black carbon (BC) mass concentration in the West African monsoon (WAM) area. BC was measured with a micro-aethalometer integrated in the payload bay of the unmanned research aircraft ALADINA (Application of Light-weight Aircraft for Detecting IN situ Aerosol). As part of the DACCIWA (Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa) project, 53 measurement flights were carried out at Savè, Benin, on 2–16 July 2016. A high variability of BC (1.79 to 2.42±0.31 µg m−3) was calculated along 155 vertical profiles that were performed below cloud base in the atmospheric boundary layer (ABL). In contrast to initial expectations of primary emissions, the vertical distribution of BC was mainly influenced by the stratification of the ABL during the WAM season. The article focuses on an event (14 and 15 July 2016) which showed distinct layers of BC in the lowermost 900 m above ground level (a.g.l.). Low concentrations of NOx and CO were sampled at the Savè supersite near the aircraft measurements and suggested a marginal impact of local sources during the case study. The lack of primary BC emissions was verified by a comparison of the measured BC with the model COSMO-ART (Consortium for Small-scale Modelling–Aerosols and Reactive Trace gases) that was applied for the field campaign period. The modelled vertical profiles of BC led to the assumption that the measured BC was already altered, as the size was mainly dominated by the accumulation mode. Further, calculated vertical transects of wind speed and BC presume that the observed BC layer was transported from the south with maritime inflow but was mixed vertically after the onset of a nocturnal low-level jet at the measurement site. This report contributes to the scope of DACCIWA by linking airborne BC data with ground observations and a model, and it illustrates the importance of a more profound understanding of the interaction between BC and the ABL in the WAM region.

scholarly journals Monitoring atmospheric particulate matters using vertically resolved measurements of a polarization lidar, in-situ recordings and satellite data over Tehran, Iran

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hossein Panahifar ◽  
Ruhollah Moradhaseli ◽  
Hamid Reza Khalesifard
Keyword(s):  
Boundary Layer ◽  
Atmospheric Aerosols ◽  
Urban Pollution ◽  
Ground Level ◽  
Dust Particles ◽  
Depolarization Ratio ◽  
Backscatter Coefficient ◽  
Dust Events ◽  
The City

AbstractThe highly polluted atmosphere above Tehran has been investigated by using a polarization lidar operating at 532 nm, in-situ particulate matter suites distributed over the city, and meteorological observations. The measurement campaign is conducted from Nov. 2014 to Jan. 2016. Three typical cases are studied in detail where, the atmosphere is polluted with urban pollution, mixture of urban pollution and dust particles from local sources, and long range transported dust from the Arabian Peninsula. For these cases, vertical profiles of the lidar backscatter coefficient, extinction coefficients, particle depolarization ratio ($$\delta _{\text {p}}$$ δ p ) and mass concentrations of atmospheric aerosols (separated into dust and non-dust particles) are presented. Using the lidar recordings, variations of the planetary boundary layer height above the city are investigated along the year. During November to February, lidar profiles frequently show polluted boundary layers that are reaching up to 1 km above the ground level. The depolarization ratio ($$\delta _{\text {p}}$$ δ p ) varies between 0.04 and 0.08 in the polluted boundary layer. During the campaign, for 103 days the urban pollution was dominant, 45 recorded dust events ($$0.15<\delta _{\text {p}}<0.20$$ 0.15 < δ p < 0.20 ) were originated from the dry regions in the south of Tehran and 15 dust events ($$0.20<\delta _{\text {p}}<0.35$$ 0.20 < δ p < 0.35 ) impacted the city that were originated from the Arabian Desert and Mesopotamia.

High-latitude precipitation: Snowfall regimes at two distinct sites in Scandinavia

2021 ◽  
Author(s):  
Julia A. Shates ◽  
Claire Pettersen ◽  
Tristan S. L’Ecuyer ◽  
Steve J. Cooper ◽  
Mark S. Kulie ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Large Scale ◽  
Ground Level ◽  
Low Pressure ◽  
Small Particles ◽  
Radar Echo ◽  
High Concentrations ◽  
Remote Sensing Methods ◽  
Rain Radar

AbstractThe prevailing snowfall regimes at two Scandinavian sites, Haukeliseter, Norway and Kiruna, Sweden, are documented using ground-based in-situ and remote sensing methods. Micro Rain Radar (MRR) profiles indicate three distinct snowfall regimes occur at both sites: shallow, deep, and intermittent snowfall. The shallow snowfall regime produces the lowest mean snowfall rates and radar echo tops are confined below 1.5 km above ground level (AGL). Shallow snowfall occurs under areas of large scale subsidence with a moist boundary layer and dry air aloft. The atmospheric ridge coinciding with shallow snowfall is highly anomalous over Haukeliseter, but is more common in Kiruna where shallow snowfall was frequently observed. The shallow snowfall particle size distributions (PSDs) are broad with lower particle concentrations than other regimes, especially small particles. Deep snowfall events exhibit MRR profiles that extend above 2 km AGL, and tend to be associated with weak low pressure and high relative humidity throughout the troposphere. The PSDs in deep events are narrower with high concentrations of small particles. Increasing MRR reflectivity towards the surface suggests aggregation as a possible growth process during deep snowfall events. The heaviest mean snowfall rates are associated with intermittent events that are characterized by deep MRR profiles, but have variations in intensity and height. The intermittent regime is associated with anomalous, deep low pressure along the coast of Norway, and enhanced relative humidity at lower levels. The PSDs reveal high concentrations of small and large particles. The analysis reveals that there are unique characteristics of shallow, deep, and intermittent snowfall regimes that are common between the sites.

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