| 13 Jul 2026
Downslope windstorms in southeast Greenland – part I: Definition, seasonality, and regional characteristics of piteraq events
Abstract. Piteraq events are strong downslope windstorms in southeast Greenland that often damage infrastructure and disrupt transport and subsistence activities of local communities. These wind events are more intense and common in winter than in summer, but with enhanced global warming and declining sea ice in the Arctic, their summer characteristics may become more relevant in the future. Using data from six weather stations and radiosonde data in the region around Tasiilaq in southeast Greenland since 1958 along with local media sources, we explore the evolution, regional variability, and local consequences of piteraq events, focusing on seasonal characteristics. Motivated by operational warning procedures and previous studies, we propose a robust definition of a piteraq based on local wind speed and direction that comprises most reported media reports on piteraq events. Using this definition, we find that the imprint of piteraq events cover regional scales of several 100 km by intensifying the wind speed around eastern slopes of the Greenland Ice Sheet and/or shifting the wind direction to down from the ice sheet. Prior to the piteraq events, the wind around Tasiilaq often turns clockwise from nearly parallel to the coast (from southwest) to down the ice sheet (from northwest), particularly at higher elevations that are less disturbed by topography. In Tasiilaq, the main seasonal differences during the developing and mature phases of a piteraq event are a substantially larger local reduction in relative humidity in summer compared to winter and also a relative warming during summer events as opposed to a relative cooling during winter events. These differences in temperature and relative humidity are likely associated with foehn mechanisms that become more common when more moisture is transported to higher levels in summer, combined with reduced regional sea ice in summer and hence larger moisture contrasts between maritime and continental air masses. Both are factors that are expected to become more dominant in a future climate. Our findings highlight the importance of understanding piteraq events in a spatial and temporal perspective for a better integration in early warning systems in the present and future climate.
Review of
Downslope windstorms in southeast Greenland - part I: Definition, seasonality, and regional characteristics of piteraq events
by Flacké Haualand and others
General
This is Part 1 of a study of the forcing (thermo-)dynamics of piteraq winds in southeast Greenland, using a combined observational and modelling approach. The paper aims to systematically define and explore downslope windstorms in southeast Greenland, identified as piteraq events, by combining in situ near-surface observations from six automatic weather stations and vertical radio soundings in the region around Tasiilaq. In addition, these piteraq events are evaluated for societal importance using media reports retrieved from various archives.
The paper succeeds in conveying the large inter-event variability of piteraqs in a reasonably clear way. I most liked the sections where inter-AWS along-surface differences and vertical profiles are presented, which could serve as a basis for a more quantitative analysis, but here also the discussion remained rather descriptive. Unfortunately, I often stumbled upon formulations that were quite frequently inaccurate, which negatively impacts the readability, see below for a non-exhaustive listing. The section on piteraq impacts from media events comes across as somewhat disconnected and does not really add substance to the paper.
Sorry, but in view of the above I do not recommend publishing this manuscript as a separate paper. At the request of the editor I also reviewed Part 2 of this paper. That part is based on CARRA re-analysis and uses the events identified in this study. A natural solution would be to merge both parts into a single study, by adding the parts about the selection criteria from this paper as a new section to Part 2.
Major comments
l. 3: "...but with enhanced global warming and declining sea ice in the Arctic, their summer characteristics may become more relevant in the future"; without further knowledge this is unclear, unless for the Piteraq area current summers look like future winters, which in many respects (e.g. radiation balance) is not the case.
Figure 1: I presume this has been attempted by the authors, but having the same colour scales for the wind roses in b) and c) would make them easier to comapre and hence interpret.
l. 79: " horizontal and vertical weather characteristics" this is inaccurately formulated; do you mean "horizontal and vertical gradients in meteorological variables"?
l. 94: Are the 1/3 hourly wind data instantaneous or averaged? How were the 1-hourly and 3-hourly Tasiilaq wind data combined? Is this mentioned in line 166? Please organise text in such a way that this information is grouped in single location.
l. 118: " This seasonality of extreme wind speed is in agreement with the seasonality of piteraq frequency"; please explain the nature of the agreement and quantify it if possible.
l. 126: "...we argue that a wind speed threshold of 15 m s−1 should be used to define piteraq events at TAS..."; it is confusing that a little later there is a full section 3.2 on the defnition of piteraq events. Please organise text in such a way that all definition related issues is grouped at a single location.
l. 168: " their detection remains challenging due to data gaps"; this is again inaccurately formulated. If there are data, detection is easy, if there are no data From Tasiilaq) detection is impossible. Suggest to reformulate into something like: "Construction of a homogeneous time series of piteraq events remains challenging due to data gaps." This would also be a good place to refer to the availability of re-analysis data that can be used to fill data gaps in space and time (discussed in part 2?).
Section 3.3: This section shows that the investigation into media reports does not find a robust quantitative connection between pteraq events following the definition used here and said media reports. This can be stated more clearly at the beginning or end of the section.
Figure 5 legend and caption: "Climatology" is used here to represent all data, but I associate it with the average weather. Perhaps replace with "All data"? Same with use of "climatology" in Fig. 6 and l. 245.
l. 241: How would a lower ice sheet albedo contribute to a larger relative humidity change?
l. 280: "deep vertical scales"; change into "deep atmospheric layers" or "large vertical scales".
Minor and textual comments
l. 33: wind speed is weaker -> wind is weaker - or- wind speed is lower.
l. 166: "(see 1)": Table 1?
l. 210: What do you mean by "net change in temperature" compared to "change in temperature"?
l. 214: stronger -> higher
l. 247: elevation -> maximum elevation (?)