Re: [ferret_users] Edges and @AVG

To: ferret_users@xxxxxxxx

Subject: Re: [ferret_users] Edges and @AVG

From: Martin Schmidt <martin.schmidt@xxxxxxxxxxxxxxxxx>

Date: Wed, 26 Feb 2020 10:46:28 +0100

Arc-authentication-results: i=3; mx.google.com; arc=pass (i=2); spf=neutral (google.com: 209.85.222.197 is neither permitted nor denied by domain of martin.schmidt@xxxxxxxxxxxxxxxxx) smtp.mailfrom=martin.schmidt@xxxxxxxxxxxxxxxxx

Arc-authentication-results: i=2; mx.google.com; arc=pass (i=1 spf=pass spfdomain=io-warnemuende.de); spf=neutral (google.com: 65.153.203.170 is neither permitted nor denied by domain of martin.schmidt@xxxxxxxxxxxxxxxxx) smtp.mailfrom=martin.schmidt@xxxxxxxxxxxxxxxxx

Arc-authentication-results: i=1; mx.google.com; spf=pass (google.com: domain of martin.schmidt@xxxxxxxxxxxxxxxxx designates 192.124.245.147 as permitted sender) smtp.mailfrom=martin.schmidt@xxxxxxxxxxxxxxxxx

Arc-message-signature: i=3; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:content-language:in-reply-to:mime-version:user-agent :date:from:references:to:subject; bh=b6IMmNnaPoXWTUjDjxKSDwPU6wlO+oBuunDT9rt2FQ8=; b=pU5t3QBlq6w5PXlFmiQZaoqDOLGUO0BT9wiigeCytaloU+9LVoR+vMYu59HRTqDppm 7fHosfvZk5oj4ILvhyLoIT+febAuBKbMeUcZU4zTeupY9L/rzYFkd71UuvNSpxhZu02s Pfw8kLy0XCKHtg0rASp9d2Ae8y3XF7Bj92wDLREquEzOWs6JWMOdiLAKqYGF3g10qPXV kdUGoQwWQeCNw7AyIcIJjbC3M1bgigiR/bDaX9exoOhh2NAmjkbj7dBaCoi41YdHi3rc 8GxRvG4yGIBvVWvpSeHQdEKD/Uz/ocEpbV0Lou+zSXNDkc1vz9LcXo+/lQ2FHw0nJWZe RUQQ==

Arc-message-signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-language:in-reply-to:mime-version:user-agent:date :message-id:from:references:to:subject; bh=b6IMmNnaPoXWTUjDjxKSDwPU6wlO+oBuunDT9rt2FQ8=; b=IgvbhShmPO2ecFFXgiCEk0ebWWH3kwl/EG7Xex2Rs9lHno40ZrYXvjCi4Ys1QJTR9p 2xWPPoMgfOXFxwmhPMPH2wSlPsBnI/XbVvqmEgoRweb8o+8qdQTjCrF4nI7pg+N2sbVh TWJ7s/IWZSQJgR8aX7to7Cq0y56P6N+SDFZAYqGbU70ONAQtWDk6IBjWayVrWdGkQjkG 2Zc3LdonhhZHcZg1Ub7OTWk6+nOXwVLT9itRABPfj/wPxHTH/yUHEQ7ZJdrJ9qLRSOfW vKz+1w1gLetpog1htE8iEfE5S9yzfg4oCxk/F+KCOjjFLdUmACvnirmb9/6n/eGUo7Hz btfw==

Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-language:in-reply-to:mime-version:user-agent:date :message-id:from:references:to:subject; bh=b6IMmNnaPoXWTUjDjxKSDwPU6wlO+oBuunDT9rt2FQ8=; b=J+BDJ4HZo6l4Q0zuPWn0O8eZzEC8+uhWh/AvI/T7ZTsQy5JsRkX2JErefCctt9rNkZ FRP0JSRlk1CGXqLs4CL8NaviBK1eIgq5yo2ddqVbRlxABbNZYHEbOEeWAoEe9CWsMYs9 kgHJ/Ne4jQymUSZskLhE1Qt/GitX6B8xRIjURiM3BrCWIBW39M7xZp1eaaVO4rVfM/EZ w9pvlfCws7jB5F/16RURHQZm7sSGMplMsxUa+m99yBD9ApgSmEbpiMBY3LqFZmBhDrsD pe8RFmxVpuq9q28nS3afJnAUbrz8OcleuOlRL+T4kgooQUf4wOVVMwoZiK7lme4GeV6T HpuA==

Arc-seal: i=3; a=rsa-sha256; t=1582710409; cv=pass; d=google.com; s=arc-20160816; b=Bd6GUSKNNJzGVdJpbgYoCgRzTfHBgVsgsh9k4yrDgApahm7C1IYOrvbof1b0D3vCEa rjkSZHDQDA9jprpvLyF2oqH8PfoOHtunJchs68uwro281Qf0bqZZvKVIi7IVvEBx0uMF UlE9LRV5qDupG6Ro9vu41uxPjpVjqR9TrwJ5GFDB7oab/x4oAAzsRYotlqm04y5l7kjx mIiQr60snnLpsHYJOMWGn4DZHdtUGnFwQsaSZrxSSAgaW00zvuKmMFKQogZYqDO3GfGb RIGitffUghxLIMEaHSV0eWzdLfhlZP4dB7uvyxwsVH1J5KIUuvgkPu6lgwcfoqmbWzdd CFHQ==

Arc-seal: i=2; a=rsa-sha256; t=1582710400; cv=pass; d=google.com; s=arc-20160816; b=D6GXYWVadL/YTovCK/kQgztFTu8wUYiQbxKN3DAMnVxgTdnmlb+XtTB4byC4ZtGkEv qWmQ0xPSmXfmcAsmShdfn1QgOE7ZGUHAyEza9v2BWg2rM/XlgRbYQEpmHVcN1lsZfPHu 4UAVqycGeib+k3bWPdHcVwrZV+sGJt8WNLf6pAsrR3CO8EEDtylOOo4Z1BXEtmZ9OUom sEuYVz7xjSmI7QXwmgyKNlFWiAxQ6+2ne5ShQbhV2Bh0f1uZVcdqlO3u4lD+bQiNgdVC BJlBs9VDcKQvYPJIdLP1z8CuDz2i4432ciW3b3aHznpfQ5xNrvXdCeMdgNHfbDjPkHBC fneg==

Arc-seal: i=1; a=rsa-sha256; t=1582710397; cv=none; d=google.com; s=arc-20160816; b=C1ZPx+B7lR9lkY0j3ryi76OW012h2khzLbujmP0+bAkcn9VcaQKYHvoXhagmVdavWW JPb42mkVRFU/cu4Kn16iHOKZh4DkPs8lWHr7Dumupwix3/xz0kjIzfgHFwyaTewBEVZ1 zbpOiX05ChT8EOaUSOG7yAxy8280s1SsZvJVo5d5qM+JeBtTmRK7oXTdWuLKqWiTwdAF IE7XxY9yLSM4CRLF1W7NWLOVvC7gIwdHUkajjGREe0eQv8NjP2f2AyvK0Am7UbH7tYbw /3/EB6Hu4PJm6MLZqTA4zY5dnFg+bjtDvzqB2G0rk2CppXYyVk6u4TcKvgXJ59Ddu/Vm nLNg==

Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=noaa.gov; s=google; h=sender:subject:to:references:from:date:user-agent:mime-version :in-reply-to:content-language:message-id:x-original-sender :x-original-authentication-results:precedence:mailing-list:list-id :list-post:list-help:list-archive; bh=b6IMmNnaPoXWTUjDjxKSDwPU6wlO+oBuunDT9rt2FQ8=; b=cVOL/oQHNk3Ne1Zvu5AuUEhFJVRyFPEt4eZctYSKnSvhuFrSG+1GuvOxolQSHl9ZPU cBOye/xtRp/3CZIkPe+KBwZVHJkAxJNt4k67NdBg4N+9s7DqzNuz6efDhHg/KAKaAa6W VylgGF94lZN4SbofFLAhJTW3FfzZNkKl6dWvRA0CAMlINAa2jsNcK5DTuZDjilnrhd93 ZU3cQM32G7tTGH8qeHWR1S9GzCLmbofT7IM/wupJcaAUC01rugpL3JQXJcAIgfhQgxew bIR6EyLpQKPn+9M2n0D2ZOb8iZU88/ZVX8qgq7mo2ZIIHe3dYEQ8CsDaW+dS7lY0amHB T+Fg==

In-reply-to: <CAEwQpa+wup6dqUCs_cQ2x3Djf59d5L5pMB4AeyHDdEFOat2otQ@mail.gmail.com>

List-archive: <https://groups.google.com/a/noaa.gov/group/ferret_users/>

List-help: <https://support.google.com/a/noaa.gov/bin/topic.py?topic=25838>, <mailto:ferret_users+help@noaa.gov>

List-id: <ferret_users.noaa.gov>

List-post: <https://groups.google.com/a/noaa.gov/group/ferret_users/post>, <mailto:ferret_users@noaa.gov>

Mailing-list: list ferret_users@xxxxxxxx; contact ferret_users+owners@xxxxxxxx

References: <CAP06G6Qt-GLxUqLY0AA+aHEEVq_3wTKhB6cLC3yFeMVtUjOVcg@mail.gmail.com> <CAEwQpa+SgCVR19G5bx2KXzNOKOKV52N7068YiTcU-rbEHrDQTA@mail.gmail.com> <CAP06G6QuNKn59BwAS7udR3i5Ef37dhEo74ku5xy95f_LxeSb5Q@mail.gmail.com> <AEB9D751-C106-4BDC-8808-4313B0CE067E@noaa.gov> <CAP06G6SmYC+TsgacshQEk2+44o=eb8d9sSkQo1xh3LxKA=9BRA@mail.gmail.com> <CAEwQpa+wup6dqUCs_cQ2x3Djf59d5L5pMB4AeyHDdEFOat2otQ@mail.gmail.com>

Sender: owner-ferret_users@xxxxxxxx

User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.1

Hi all,

in the context of long time series, the word "time stamp" also was used differently:

Imagine you are living some time ago and are running a mechanically recording thermometer scratching a curve into wax paper. Every month you put in a new roll of that wax paper and put the previous one into the cubicle . To indentify it, you make a "time stamp" on it just marking the day when you took it out. So in some data sets the time stamp marks the end of a measuring period.

People producing data, especially time series, are often living in a scientific environment with different conventions like those using the data. But all are using the same words and are not aware of possible sources of misunderstanding. Even in times of netcdf with many meta data attached to the data, the very meaning of the numbers may be unclear and can be even lost over time. So it is very important, to have some communication between these different worlds.

I remember that the data set in question her is related to era-5. So its worth to read the era-5 description in the COPERNICUS portal.

A mirror is here:

If this does not answer the question, it's definitely worth to ask there for support. I did this some time ago for a similar problem with ncep and got friendly and helpful answers.

Greetings,

Martin

On 2/26/20 3:04 AM, Ryo Furue wrote:

Hi Alexander and Ferret fans,

On Wed, Feb 26, 2020 at 7:15 AM Alexander Audet <alexander.c.audet@xxxxxxxxx> wrote:

As far as I can tell (link) although the monthly means are timestamped at the first of the month and seem to be centered there, they actually represent the average value of the month instead 1/2 the last and 1/2 the named month. I am still confused about this, so I could be wrong.

If this netCDF file was created by some respectable organization, you may want to file a bug report. This error affects a lot of users. The best netCDF configuration for a monthly-mean dataset is, I think, such that

- Each monthly mean is defined at the center of the month.

- The "time_bnds" coordinate variable correctly specifies the beginning and end of each month ( http://cfconventions.org/cf-conventions/cf-conventions.html ).

Having said all that, it all depends on how accurate you want your seasonal means to be. For many use cases, the simple (unweighted) average may be fine. In that case, the 3-point boxcar average (is that @SBX ?) on the L axis will do.

Regards,

Ryo